#include<bits/stdc++.h>
using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<int> a(n + 5, 0);
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    sort(a.begin() + 1, a.begin() + n + 1);
    int ans = 0, cnt = 0;
    for (int i = 1; i <= n - ans; i++)
    {
        if (i > a[i+ans])
            while (true)
            {
                ans++;
                if (i<=a[i+ans])
                {
                    cnt++;
                    break;
                }
            }
        else
            cnt++;
    }
    cout << cnt;
}