#include <bits/stdc++.h>
#define int long long

using namespace std;

const int N = 1e5 + 10;
typedef pair<int, int> PII;
map<int, int> d[N];
vector<int> g[N];
bool b[N];
void solve() {
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        g[b].push_back(a);
        d[a]++, d[b]++;
    }
    queue<int> q;
    cout << 0 << endl;
    for (auto [pos, num] : d)
        if (num == 1) {
            q.push(pos);
            b[pos] = 1;
        }
    while (q.size()) {
        int u = q.front();
        q.pop();
        for (auto ele : g[u]) {
            if (!b[ele]) {
                d[ele]--;
                cout << u << ' ' << ele << endl;
                if (d[ele] == 1)
                    q.push(ele), b[ele] = 1;
            }
        }
    }
    for (auto [pos, num] : d) {
        if (!b[pos]) {
            d[pos]--;
            b[pos] = 1;
        }
    }
    while (q.size()) {
        int u = q.front();
        q.pop();
        for (int i = 0; i < g[u].size(); i++) {
            int ele = g[u][i];
            if (!b[ele]) {
                cout << u << ' ' << ele << endl;
                d[ele]--;
                q.push(ele);
                b[ele] = 1;
                break;
            }
        }
    }
}
signed main() {
    ios::sync_with_stdio(0), cout.tie(0), cin.tie(0);
    int t = 1;
    //	cin>>t;
    while (t--) solve();
    return 0;
}

/sandbox/1/a.cpp: In function 'void solve()':
/sandbox/1/a.cpp:17:7: error: no 'operator++(int)' declared for postfix '++' [-fpermissive]
   17 |   d[a]++,d[b]++;
      |   ~~~~^~
/sandbox/1/a.cpp:17:14: error: no 'operator++(int)' declared for postfix '++' [-fpermissive]
   17 |   d[a]++,d[b]++;
      |          ~~~~^~
/sandbox/1/a.cpp:21:11: error: cannot decompose inaccessible member 'std::map<long long int, long long int>::_M_t' of 'std::map<long long int, long long int>'
   21 |  for(auto [pos,num]:d)
      |           ^~~~~~~~~
In file included from /usr/include/c++/10/map:61,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:81,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/stl_map.h:153:17: note: declared private here
  153 |       _Rep_type _M_t;
      |                 ^~~~
/sandbox/1/a.cpp:31:11: error: no 'operator--(int)' declared for postfix '--' [-fpermissive]
   31 |     d[ele]--;
      |     ~~~~~~^~
/sandbox/1/a.cpp:33:14: error: no match for 'operator==' (operand types are 'std::map<long long int, long long int>' and 'int')
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |        ~~~~~~^~~
      |             |  |
      |             |  int
      |             std::map<long long int, long long int>
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:1035:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const std::__cxx11::sub_match<_BiIter>&)'
 1035 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:1035:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:1131:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const std::__cxx11::sub_match<_BiIter>&)'
 1131 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:1131:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:1206:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1206 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:1206:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:1298:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const std::__cxx11::sub_match<_BiIter>&)'
 1298 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:1298:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:1373:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1373 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:1373:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:1466:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const std::__cxx11::sub_match<_BiIter>&)'
 1466 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:1466:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:1545:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1545 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:1545:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/regex:62,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:110,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/regex.h:2101:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const std::__cxx11::match_results<_BiIter, _Alloc>&, const std::__cxx11::match_results<_BiIter, _Alloc>&)'
 2101 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/10/bits/regex.h:2101:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/stl_algobase.h:64,
                 from /usr/include/c++/10/bits/specfun.h:45,
                 from /usr/include/c++/10/cmath:1927,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:41,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/stl_pair.h:466:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)'
  466 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/10/bits/stl_pair.h:466:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::pair<_T1, _T2>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/stl_algobase.h:67,
                 from /usr/include/c++/10/bits/specfun.h:45,
                 from /usr/include/c++/10/cmath:1927,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:41,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/stl_iterator.h:360:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)'
  360 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/10/bits/stl_iterator.h:360:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/stl_algobase.h:67,
                 from /usr/include/c++/10/bits/specfun.h:45,
                 from /usr/include/c++/10/cmath:1927,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:41,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/stl_iterator.h:398:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)'
  398 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/10/bits/stl_iterator.h:398:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/stl_algobase.h:67,
                 from /usr/include/c++/10/bits/specfun.h:45,
                 from /usr/include/c++/10/cmath:1927,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:41,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/stl_iterator.h:1427:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)'
 1427 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/10/bits/stl_iterator.h:1427:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::move_iterator<_IteratorL>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/stl_algobase.h:67,
                 from /usr/include/c++/10/bits/specfun.h:45,
                 from /usr/include/c++/10/cmath:1927,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:41,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/stl_iterator.h:1495:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)'
 1495 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/10/bits/stl_iterator.h:1495:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::move_iterator<_IteratorL>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/iosfwd:40,
                 from /usr/include/c++/10/ios:38,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/postypes.h:222:5: note: candidate: 'template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)'
  222 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/10/bits/postypes.h:222:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::fpos<_StateT>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/string:41,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/allocator.h:206:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_T2>&)'
  206 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/10/bits/allocator.h:206:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::allocator<_CharT>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/basic_string.h:48,
                 from /usr/include/c++/10/string:55,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/string_view:490:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::basic_string_view<_CharT, _Traits>)'
  490 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/10/string_view:490:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/basic_string.h:48,
                 from /usr/include/c++/10/string:55,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/string_view:496:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::__type_identity_t<std::basic_string_view<_CharT, _Traits> >)'
  496 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/10/string_view:496:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/basic_string.h:48,
                 from /usr/include/c++/10/string:55,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/string_view:519:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(std::__type_identity_t<std::basic_string_view<_CharT, _Traits> >, std::basic_string_view<_CharT, _Traits>)'
  519 |     operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
      |     ^~~~~~~~
/usr/include/c++/10/string_view:519:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/string:55,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/basic_string.h:6153:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&, const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 6153 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/basic_string.h:6153:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/string:55,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/basic_string.h:6161:5: note: candidate: 'template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::__cxx11::basic_string<_CharT>&, const std::__cxx11::basic_string<_CharT>&)'
 6161 |     operator==(const basic_string<_CharT>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/basic_string.h:6161:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::basic_string<_CharT>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/string:55,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/basic_string.h:6175:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
 6175 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/basic_string.h:6175:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/string:55,
                 from /usr/include/c++/10/bits/locale_classes.h:40,
                 from /usr/include/c++/10/bits/ios_base.h:41,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/basic_string.h:6216:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 6216 |     operator==(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/10/bits/basic_string.h:6216:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'const _CharT*' and 'std::map<long long int, long long int>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/ios_base.h:46,
                 from /usr/include/c++/10/ios:42,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/system_error:342:3: note: candidate: 'bool std::operator==(const std::error_code&, const std::error_code&)'
  342 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/10/system_error:342:32: note:   no known conversion for argument 1 from 'std::map<long long int, long long int>' to 'const std::error_code&'
  342 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/10/system_error:349:3: note: candidate: 'bool std::operator==(const std::error_code&, const std::error_condition&)'
  349 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/10/system_error:349:32: note:   no known conversion for argument 1 from 'std::map<long long int, long long int>' to 'const std::error_code&'
  349 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/10/system_error:357:3: note: candidate: 'bool std::operator==(const std::error_condition&, const std::error_condition&)'
  357 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/10/system_error:357:37: note:   no known conversion for argument 1 from 'std::map<long long int, long long int>' to 'const std::error_condition&'
  357 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/10/system_error:390:3: note: candidate: 'bool std::operator==(const std::error_condition&, const std::error_code&)'
  390 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/10/system_error:390:37: note:   no known conversion for argument 1 from 'std::map<long long int, long long int>' to 'const std::error_condition&'
  390 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/10/bits/locale_facets.h:48,
                 from /usr/include/c++/10/bits/basic_ios.h:37,
                 from /usr/include/c++/10/ios:44,
                 from /usr/include/c++/10/istream:38,
                 from /usr/include/c++/10/sstream:38,
                 from /usr/include/c++/10/complex:45,
                 from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/streambuf_iterator.h:227:5: note: candidate: 'template<class _CharT, class _Traits> bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)'
  227 |     operator==(const istreambuf_iterator<_CharT, _Traits>& __a,
      |     ^~~~~~~~
/usr/include/c++/10/bits/streambuf_iterator.h:227:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::istreambuf_iterator<_CharT, _Traits>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/complex:463:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const std::complex<_Tp>&, const std::complex<_Tp>&)'
  463 |     operator==(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/10/complex:463:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::complex<_Tp>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/complex:468:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const std::complex<_Tp>&, const _Tp&)'
  468 |     operator==(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/10/complex:468:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::complex<_Tp>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:54,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/complex:474:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const _Tp&, const std::complex<_Tp>&)'
  474 |     operator==(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/10/complex:474:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/tuple:39,
                 from /usr/include/c++/10/functional:54,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/array:253:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> bool std::operator==(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)'
  253 |     operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
      |     ^~~~~~~~
/usr/include/c++/10/array:253:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::array<_Tp, _Nm>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/functional:54,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/tuple:1393:5: note: candidate: 'template<class ... _TElements, class ... _UElements> constexpr bool std::operator==(const std::tuple<_Tps ...>&, const std::tuple<_UTypes ...>&)'
 1393 |     operator==(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/10/tuple:1393:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::tuple<_Tps ...>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/functional:59,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/std_function.h:680:5: note: candidate: 'template<class _Res, class ... _Args> bool std::operator==(const std::function<_Res(_ArgTypes ...)>&, std::nullptr_t)'
  680 |     operator==(const function<_Res(_Args...)>& __f, nullptr_t) noexcept
      |     ^~~~~~~~
/usr/include/c++/10/bits/std_function.h:680:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::function<_Res(_ArgTypes ...)>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/functional:59,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/std_function.h:687:5: note: candidate: 'template<class _Res, class ... _Args> bool std::operator==(std::nullptr_t, const std::function<_Res(_ArgTypes ...)>&)'
  687 |     operator==(nullptr_t, const function<_Res(_Args...)>& __f) noexcept
      |     ^~~~~~~~
/usr/include/c++/10/bits/std_function.h:687:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'const std::function<_Res(_ArgTypes ...)>' and 'int'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/node_handle.h:39,
                 from /usr/include/c++/10/bits/hashtable.h:37,
                 from /usr/include/c++/10/unordered_map:46,
                 from /usr/include/c++/10/functional:61,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/optional:985:5: note: candidate: 'template<class _Tp, class _Up> constexpr std::__optional_relop_t<decltype ((declval<_Tp>() == declval<_Up>()))> std::operator==(const std::optional<_Tp>&, const std::optional<_Up>&)'
  985 |     operator==(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/10/optional:985:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::optional<_Tp>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/node_handle.h:39,
                 from /usr/include/c++/10/bits/hashtable.h:37,
                 from /usr/include/c++/10/unordered_map:46,
                 from /usr/include/c++/10/functional:61,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/optional:1045:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const std::optional<_Tp>&, std::nullopt_t)'
 1045 |     operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept
      |     ^~~~~~~~
/usr/include/c++/10/optional:1045:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::optional<_Tp>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/node_handle.h:39,
                 from /usr/include/c++/10/bits/hashtable.h:37,
                 from /usr/include/c++/10/unordered_map:46,
                 from /usr/include/c++/10/functional:61,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/optional:1056:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(std::nullopt_t, const std::optional<_Tp>&)'
 1056 |     operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept
      |     ^~~~~~~~
/usr/include/c++/10/optional:1056:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'const std::optional<_Tp>' and 'int'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/node_handle.h:39,
                 from /usr/include/c++/10/bits/hashtable.h:37,
                 from /usr/include/c++/10/unordered_map:46,
                 from /usr/include/c++/10/functional:61,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/optional:1113:5: note: candidate: 'template<class _Tp, class _Up> constexpr std::__optional_relop_t<decltype ((declval<_Tp>() == declval<_Up>()))> std::operator==(const std::optional<_Tp>&, const _Up&)'
 1113 |     operator==(const optional<_Tp>& __lhs, const _Up& __rhs)
      |     ^~~~~~~~
/usr/include/c++/10/optional:1113:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   'std::map<long long int, long long int>' is not derived from 'const std::optional<_Tp>'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/bits/node_handle.h:39,
                 from /usr/include/c++/10/bits/hashtable.h:37,
                 from /usr/include/c++/10/unordered_map:46,
                 from /usr/include/c++/10/functional:61,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/optional:1119:5: note: candidate: 'template<class _Tp, class _Up> constexpr std::__optional_relop_t<decltype ((declval<_Up>() == declval<_Tp>()))> std::operator==(const _Up&, const std::optional<_Tp>&)'
 1119 |     operator==(const _Up& __lhs, const optional<_Tp>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/10/optional:1119:5: note:   template argument deduction/substitution failed:
/sandbox/1/a.cpp:33:16: note:   mismatched types 'const std::optional<_Tp>' and 'int'
   33 |     if(d[ele]==1)q.push(ele),b[ele]=1;
      |                ^
In file included from /usr/include/c++/10/unordered_map:47,
                 from /usr/include/c++/10/functional:61,
                 from /usr/include/c++/10/pstl/glue_algorithm_defs.h:13,
                 from /usr/include/c++/10/algorithm:74,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
                 from /sandbox/1/a.cpp:1:
/usr/include/c++/10/bits/unordered_map.h:2090:5: note: candidate: 'template<class _Key1, class _Tp1, class _Hash1, class _Pred1, class _Alloc1> bool std::operator==(const std::unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&, const std::unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&)'
 2090 |     operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
      
<44689 bytes omitted>