import java.util.*;
public class xiaowuc1 {
  public static void main(String[] args) throws Exception {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] need = new int[201];
    for(int i = 0; i < n; i++) need[sc.nextInt()]++;
    int ret = 0;
    while(n > 0) {
      ret++;
      for(int x = 0; x < ret; x++) {
        int amt = (ret - 1) + x;
        if(amt < need.length && need[amt] > 0) {
          need[amt]--;
          n--;
        }
      }
      for(int x = 0; x < ret-1; x++) {
        int amt = (ret - 1) + x;
        if(amt < need.length && need[amt] > 0) {
          need[amt]--;
          n--;
        }
      }
    }
    System.out.println(ret);
  }
}