include <bits/stdc++.h>

vector<int> a(n);
for(int i = 0; i < n; i++) cin >> a[i];

sort(a.begin(), a.end());

int h = 0;

for(int i = 0; i < n; i++) {
    if(a[i] >= h) {
        h++;
    }
}

cout << h;