标程

/*
*/
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define sqrt(a) sqrtl(a)
#define abs(a) llabs(a)
#define pow(a) powl(a)
typedef  pair<int,int> pi ;
#define if1(x) for(int i =1 ;i<=x;i++)
#define if0(x) for(int i = 0;i<x;i++)
#define jf0(x) for(int j = 0;j<x;j++)
#define jf1(x) for(int j = 1;j<=x;j++)
#define pb push_back
const int mod = 1e9+7;
const int inf = 0xFFFFFFFFFFFFFFF;
const int N = 3e5+10;

int w[N];

int difn[N];
struct Node {
    int l, r;
    int mx;
    int add; // 懒标记
} tr[4*N];

void pushup(int u) {
    //int lc = u<<1,rc = u<<1|1;
    tr[u].mx = max(tr[u<<1].mx , tr[u<<1|1].mx) ;
}
void pushdown(int u) {
    if (tr[u].add == 0) return;
    auto &root = tr[u];
    auto &left = tr[u<<1];
    auto &right = tr[u<<1|1];
    //自己已经是加过的mx了
    // tr[u].mx += root.add;

    left.add += root.add;
    right.add += root.add;
    left.mx += root.add;
    right.mx += root.add;
    root.add = 0;
    
    // root.add = 0;
    // left.sum += (left.r - left.l + 1) * root.add;
    // left.add += root.add;
    
    // right.sum += (right.r - right.l + 1) * root.add;
    // right.add += root.add;
    
    // root.add = 0;
}

void build(int u, int l, int r) {
    tr[u] = {l, r};
    if (l == r) {
        tr[u].mx = w[l];
        return;
    }
    int mid = (l + r) >> 1;
    build(u<<1, l, mid);
    build(u<<1|1, mid+1, r);
    pushup(u);
}

int query(int u, int l, int r) {
    if (l <= tr[u].l && r >= tr[u].r) {
        return tr[u].mx;
    }
    pushdown(u);
    int mid = (tr[u].l + tr[u].r) >> 1;
    int v = 0;
    if (l <= mid) {
        v = query(u<<1, l, r);
    }
    if (r > mid) {
        v = max(v,query(u<<1|1, l, r));
    }
    return v;
}

void modify(int u, int l, int r, int v) {
    if (l <= tr[u].l && r >= tr[u].r) {
        tr[u].mx += v;
        // tr[u].sum += (tr[u].r - tr[u].l + 1) * v;
        tr[u].add += v;
    } else {
        pushdown(u);
        int mid = (tr[u].l + tr[u].r) >> 1;
        if (l <= mid) {
            modify(u<<1, l, r, v);
        }
        if (r > mid) {
            modify(u<<1|1, l, r, v);
        }
        pushup(u);
    }
}

void solve(){
    int m,n;
    cin>>n;
    map<int,int > mp;
    vector<int> num(n+10);
    if1(n)cin>>num[i];
    for(int i =n;i>=1;i--){
        mp[num[i]] ++;
        difn[i] = mp.size();
    }
    mp.clear();
    build(1,1,n);
    //wi表示，0-i-1，为一段，i-now为一段
    int ans = 0;
    if1(n-1){
        int p3 = difn[i+1];
        modify(1,i,i,mp.size());
        //第二段更新
        if(!mp.count(num[i])){
            //之前没有出现过，那么所有的第二段都需要+1
            modify(1,1,i,1);
        }else{
            int p2 = mp[num[i]];
            modify(1,p2+1,i,1);
        }
        mp[num[i]] = i;
        int res = query(1,1,i);
        ans = max(ans,res+p3);
    }
    cout<<ans<<endl;

}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr); 
    int t=1;
    // cin>>t;
    while (t--)
    {
        solve();
    }
    return 0;
}
/*


*/