// two_pointers_fast_slow_

using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        LinkedList<int> ll = new LinkedList<int>();

        // Console.WriteLine(getsum(sum));

        ll.AddLast(1);

        ll.AddLast(2);

        ll.AddLast(3);

        //ll.AddLast(4);

        //ll.AddLast(5);

        //ll.AddLast(6);

        //ll.AddLast(7);

        LinkedListNode<int> slow = ll.First;

        LinkedListNode<int> fast = ll.First;

        //try

        //{

            while(fast != null && fast.Next != null)

            {

                slow = slow.Next;

                //Console.WriteLine(slow.Value);

                fast = fast.Next.Next;

            }

        //}

        //catch{}

        Console.WriteLine(slow.Value);

    }

}