using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var collect1 = new List<int> { 1,2,3 };

        var collect2 = new List<int> { 2,3,4 };

        var result = collect1.Intersect(collect2);

        Console.WriteLine(result.Aggregate(string.Empty, (str, integer) => $"{str} {integer.ToString()}"));

    }

}