MordorTrip

#include<bits/stdc++.h>
using namespace std;
ifstream fin("mordortrip.in");
ofstream fout("mordortrip.out");
int main() {

    //citirea inputului.
    long long n;
    fin >> n;
    vector<int> a(n + 1);
    for (int i = 1; i <= n; ++i) {
        fin >> a[i];
    }

    //sortarea vectorului auxiliar.
    vector<int> b = a;
    sort(b.begin() + 1, b.end(), greater<int>());
    long long ans = 0;
    for (long long i = 1; i <= n; ++i) {

        //caut binar pozitia in vectorul sortat elemntului i.
        int st = 1, dr = n;
        int rep = 0;
        while (st <= dr) {
            int mid = (st + dr) / 2;
            if (b[mid] >= a[i]) {
                st = mid + 1;
                rep = mid;
            }
            else {
                dr = mid - 1;
            }
        }
        //updatez raspunsul.
        ans = max(ans, i - rep);
    }
    fout << ans;
}