#include <iostream>
#include <sstream>
#include <cmath>

using namespace std;
string x;

int main() {
    cin >> x;
    x += ".000000";
    long long ans = 9999999999;
    long long l = 0, r = ans;
    while (l < r) {
        long long mid = l + r >> 1;
        string t = to_string(8 * pow(mid, 2) + pow(mid, 3));
        //		cout << "t: " << t << endl;
        if (t.size() > x.size() || (t.size() == x.size() && t > x))
            r = mid;
        else if (t.size() < x.size() || (t.size() == x.size() && t < x))
            l = mid + 1;
    }
    cout << l << endl;

    return 0;
}

Traceback (most recent call last):
  File "/usr/lib/python3.8/py_compile.py", line 144, in compile
    code = loader.source_to_code(source_bytes, dfile or file,
  File "<frozen importlib._bootstrap_external>", line 846, in source_to_code
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "a.py", line 5
    using namespace std;
          ^
SyntaxError: invalid syntax

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.8/py_compile.py", line 209, in main
    compile(filename, doraise=True)
  File "/usr/lib/python3.8/py_compile.py", line 150, in compile
    raise py_exc
__main__.PyCompileError:   File "a.py", line 5
    using namespace std;
          ^
SyntaxError: invalid syntax


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/usr/lib/python3.8/py_compile.py", line 218, in <module>
    sys.exit(main())
  File "/usr/lib/python3.8/py_compile.py", line 213, in main
    if quiet < 2:
NameError: name 'quiet' is not defined