#include <bits/stdc++.h>
using namespace std;
const int max_n = 105;
int n;
int a[max_n];
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", &a[i]);
  vector<int> V;
  sort(a, a + n);
  for (int nb = 1; nb <= n; nb++) {
    V.clear();
    for (int i = 0; i < nb; i++) V.push_back(a[n - i - 1]);
    bool pos = 1;
    for (int i = n - nb - 1; i >= 0; i--) {
      int mx = 0, mj = 0;
      for (int j = 0; j < nb; j++)
        if (mx < V[j]) {
          mx = V[j];
          mj = j;
        }
      if (mx > 0) {
        V[mj] = min(V[mj] - 1, a[i]);
      } else
        pos = 0;
    }
    if (pos) {
      printf("%d\n", nb);
      return 0;
    }
  }
  return 0;
}
