F7

#include <iostream>
#include <algorithm>

using namespace std;

const int MAXN = 300005;

int N;
int B[MAXN];

int rmax[MAXN];

int main() {
    cin >> N;
    for (int i = 0; i < N; ++i) {
        cin >> B[i];
    }

    sort(B, B+N);
    rmax[0] = 0;
    for (int i = 0; i < N; ++i) {
        rmax[i + 1] = max(rmax[i], B[i] + N - i + 1);
    }

    int ct = 0;
    int right = 0;
    for (int i = N - 1; i >= 0; --i) {
        if (B[i] + N >= rmax[i] && B[i] + N >= right) {
            ++ct;
        }
        right = max(right, B[i] + N - i);
    }

    cout << ct << '\n';

    return 0;
}