#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, x = -1, count = 0, y;
  cin >> n;
  int a[n];
  vector<int> v;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    v.push_back(a[i]);
  }
  sort(a, a + n);
  while (v.size() != 0) {
    int m = 0;
    v.clear();
    for (int i = 0; i < n; i++) {
      if (a[i] != -1) {
        if (a[i] >= m) {
          v.push_back(a[i]);
          a[i] = -1;
          m++;
        }
      }
    }
    if (m > 0) count++;
  }
  cout << count;
  return 0;
}
