#include <string>
#include <vector>
#include <functional> 
#include <algorithm>

using namespace std;

int solution(vector<int> citations) {
    int answer = 0;
    sort(citations.begin(), citations.end(), greater());
    
    for (auto it : citations)
    {
        if (it <= answer) break;
        answer+=1;
    }
    
    return answer;
}