#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5, M = 1e9 + 7;
int main() {
  ios ::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  vector<int> a;
  for (int i = 1; i <= n; ++i) {
    int x;
    cin >> x;
    a.push_back(x);
  }
  int ret = 0;
  while (!a.empty()) {
    ++ret;
    vector<int> del;
    sort(a.begin(), a.end());
    int cur = 0;
    for (int i = 0; i < a.size(); ++i) {
      if (a[i] >= cur) {
        del.push_back(i);
        ++cur;
      }
    }
    reverse(del.begin(), del.end());
    for (auto p : del) {
      a.erase(a.begin() + p);
    }
  }
  cout << ret;
  return 0;
}
