import java.io.PrintStream;

import java.util.Arrays;

import java.util.Comparator;

/**

* Created by Administrator on 2016/10/21 0021.

*/

public class H_Index {

public static int hIndex(int[] citations) {

int n = citations.length, i=0;

Integer citation[] = new Integer[n];

for(int a:citations){

citation[i++] = a;

}

PrintStream out = System.out;

Comparator comparator = new Comparator<Integer>() {

@Override

public int compare(Integer o1, Integer o2) {

if(o1 >= o2)return -1;

else return 1;

}

};

Arrays.sort(citation, comparator);

for(i = n - 1;i>=0;i--)

{

if(citation[i] >= i)break;

}

return citation[i];

}

public static void main(String args[]){

int a[] = {3, 0, 6, 1, 5};

PrintStream out = System.out;

int ans = hIndex(a);

out.println(ans);

}

}