代码：

#include <bits/stdc++.h>
const int N = 5e4 + 13;
int n;
int x[N];
long long ans = 0;
int main(){
	scanf("%d", &n);
	for(int i = 1; i <= n; i++){
		scanf("%d", &x[i]);
	}
	std::sort(x, x + n + 1);
	int s = 0;
	for(int i = n; i >= 1; i--){
		if(s <= 0){
			s = x[i] + 1;
			ans++;
		}
		s--;
		s = std::min(s, x[i]);
	}
	printf("%lld\n", ans);
	return 0;
}