import java.util.Arrays;

public class HIndex {

    public static int getHIndex(int[] citations){
        Arrays.sort(citations);
        for (int i = 0; i < citations.length; i++) {
            if (i + 1 > citations[citations.length - 1 - i]) {
                return i;
            }
        }
        return citations.length;
    }

    public static void main(String[] args) {
        int[] citations1 = {2, 0, 13, 24};  // 2
        int[] citations2 = {12, 6, 7, 13};  // 4
        int[] citations3 = {1, 38, 12, 3}; // 3
        System.out.println(getHIndex(citations1));
        System.out.println(getHIndex(citations2));
        System.out.println(getHIndex(citations3));
    }
}