PAT basic 1060

#include <cstdio>#include <algorithm>using namespace std;int a[1000000];bool cmp1(int a, int b) {    return a > b;}int main() {    int n;    scanf("%d", &n);    for(int i = 1; i <= n; i++) {        scanf("%d", &a[i]);    }    sort(a+1, a+n+1, cmp1);    int ans = 0;    int p = 1;    while(ans <= n && a[p] > p) {        ans++;        p++;    }    printf("%d", ans);    return 0;}