using System;

​

public class Program

{

    class Node

    {

        public int Value { get; set; }

        public Node Next { get; set; }

    }

    static Node head = null;

    static Node tail = null;

    static void addNode(int val)

    {

        Node newNode = new Node();

        newNode.Value = val;

        if (head == null)

        {

            head = newNode;

            tail = head;

        }

        else

        {

            tail.Next = newNode;

            tail = newNode;

        }

    }

    static void printList()

    {

        Node ptr = head;

        Console.WriteLine();

        while (ptr != null)

        {

            Console.Write($" {ptr.Value} ");

        }

        Console.WriteLine();

    }

    static void reverse()

    {

        Node prev;

        Node curr;

        Node next;

        prev = null;

        curr = head;

        while (curr != null)

        {

            next = curr.Next;

            curr.Next = prev;

            prev = curr;

            curr = next;

        }

    }

    public static void Main()

    {

        addNode(1);

        addNode(2);

        addNode(3);

        addNode(4);

        addNode(5);

    }

}