using System;

public class Program

{

    public static void Main()

    {

        int a,b;

        Console.WriteLine("how big you want your arr to be?");

        a=int.Parse(Console.ReadLine());

        Console.WriteLine("how big you want your arr2 to be?");

        b=int.Parse(Console.ReadLine());

        int[] arr=new int[a];

        int[] arr2=new int[b];

        int[] arr3=new int[a+b];

        Console.WriteLine("what are the numbers you want for arr:");

        for(int i=0; i<a; i++)

        {

            arr[i]=int.Parse(Console.ReadLine());

        }

        Console.WriteLine("what are the numbers you want for arr2:");

        for(int i=0; i<b; i++)

        {

            arr2[i]=int.Parse(Console.ReadLine());

        }

        //the check

        for(int i=0; i<b; i++)

        {

            for(int j=0; j<a; j++)

            {

                if(arr[j] == arr2[i])

                {

                    arr3[i] = arr[j];

                    Console.WriteLine("the numbers that are linked are:" + arr3[i]);

                }

            }

        }

    }

}

​