using System;

public class Program

{

    public static void Main()

    {

        var a = new item{ id=1};

        var b = new item{ id=2, Next= a};

        var c = new item {id=3, Next= b};

        var d = new item{ id= 4,Next =c};

        var t = item.rev(d);

        while(a != null){

            Console.WriteLine(a.id);

            a = a.Next;

        }

    }

}

public class item{

    public int id;

    public item Next;

    public static item rev(item it){

        if (it== null|| it.Next== null)

            return it;

        var nx = rev(it.Next);

        nx.Next = it;

        it.Next = null;

    //  Console.WriteLine("it:i {0}  nx: {1}",nx.id,it.id);

        return it;

        }

}