Task C

#include <bits/stdc++.h>
#define int int64_t

using namespace std;

int32_t main()
{
    int n;
    cin >> n;
    int a[n];
    for(auto &i: a)
        cin >> i;
    sort(a, a + n);
    int now = n;
    int ans = -1;
    for(int i = 0; i < n; i++)
        ans = max((int)ans, (int)min(now, a[i])), now--;
    cout << ans;
}