1117 Eddington Number （25 分）

British astronomer Eddington liked to ride a bike. It is said that in order to show off his skill, he has even defined an "Eddington number", E -- that is, the maximum integer E such that it is for E days that one rides more than E miles. Eddington's own E was 87.

Now given everyday's distances that one rides for N days, you are supposed to find the corresponding E (≤N).

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (≤10​5​​), the days of continuous riding. Then N non-negative integers are given in the next line, being the riding distances of everyday.

Output Specification:

For each case, print in a line the Eddington number for these N days.

Sample Input:

10
6 7 6 9 3 10 8 2 7 8

Sample Output:

6

#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 100010;

bool cmp(int a,int b){
    return a > b;
}

int main(){
    int n;
    scanf("%d",&n);
    int arr[maxn];
    for(int i = 1; i <= n; i++){
        scanf("%d",&arr[i]);
    }
    sort(arr+1,arr+n+1,cmp);
  int E = 1;
  while(E <= n && arr[E] > E) E++;
  printf("%d",E-1);
    return 0;
}