include<bits/stdc++.h>

using namespace std;

int a[1000005]; int count1[1000005];

int main(){

int n;
cin >> n;
int max = -1;
for(int i = 0; i < n; i++){
	int x;
	cin >> x;
	if(x > max) max = x;
	count1[x]++;
}
int res = 0;
int day = 0;
int index = 0;
while(day <= max){
	for(int i = day; i <= max; i++){
		if(count1[i] > 0){
			count1[i]--;
			res++;
			break;
		}
	}
	day++;
}
cout << res;

}