using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        List<int> a = new List<int>();

        List<int> b = new List<int>();

        Change(a, ref b);

        Console.WriteLine(a.Count);

        Console.WriteLine(b.Count);

    }

    public static void Change (List<int> first, ref List<int> second)

    {

        first.Add(1);

        first.Add(2);

        second.Add(3);

        second.Add(4);

        first = null;

        second = null;

    }

}