Help Mocha - JAVA

package com.company;

import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;


public class Problem {

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[][] likes = new int[n][2];

        for(int i=0; i < n; i++){
            likes[i][0] = sc.nextInt();
            likes[i][1] = sc.nextInt();
        }
        int[] result_array = helpMocha(likes, n);
        for(int a : result_array)
            System.out.print(a + " ");
        System.out.println();
    }


    public static int[] helpMocha(int[][] likes, int n) {
        HashMap<Integer, HashSet<Integer>> mp = new HashMap<>();
        HashSet<Integer> resultSet = new HashSet<>();

        for (int[] like : likes) {
            if (!mp.containsKey(like[0])) {
                mp.put(like[0], new HashSet<>());
            }
            HashSet<Integer> temp = mp.get(like[0]);
            temp.add(like[1]);
            mp.put(like[0], temp);

            if (mp.containsKey(like[1]) && mp.get(like[1]).contains(like[0])) {
                resultSet.add(like[0]);
                resultSet.add(like[1]);
            }
        }

        if(resultSet.isEmpty())
            return new int[]{-1};

        int[] result_array = new int[resultSet.size()];
        int i=0;
        for(int a : resultSet){
            result_array[i] = a;
            i++;
        }

        Arrays.sort(result_array);
        return result_array;
    }
}