using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var x = new int[] { 1, 5, 3, 4, 2, 9, 10 };

        var y = new int [] {54, 3, 13, 1, 6, 7, 10, 54, 32 };

        var z = Intersect(x, y);

        foreach (var num in z) {

            Console.WriteLine(num); 

        }

    }

    public static int[] Intersect(int[] arr1, int[] arr2) {

        var diction = new Dictionary<int, int>();

        int count = 0;

        foreach (var num in arr2) {

            if (diction.ContainsKey(num)) {

                diction[num] -= 1;

            } else {

                diction.Add(num, 1);    

            }

        }

        foreach (var num in arr1) {

            if (diction.ContainsKey(num)) {

                diction[num] += 1;

                count++;

            } else {

                diction.Add(num, 1);

            }

        }

        var returnArray = new int[count];

        var index = 0;

        foreach (var elem in diction) {

            if (elem.Value > 1) {

                returnArray[index] = elem.Key;

                index++;

            }

        }

        return returnArray;

    }

}