using System;

    class CustomLinkedList{

        //Attribute- Head of the Linked List

        Node head;

        public class Node

        {

            //Every Node has two attributes - data and a pointer

            public int data;

            public Node next;

            //Constrctor

            public Node(int d)

            {

                data = d;

            }

        }

    public void deleteBackHalf()

    {

        if(head == null && head.next == null)

        {

            //In this case, list can have null or one element, so in both cases we can assign the head to null

            head = null;

        }

        //Iterate through ll

        //when we reach middle node, we assign its next reference to null

        //To get the middle element we need two pointers

        //fast will move 2wice as fast as slow pointer

        Node slow = head;

        Node fast = head;

        //prev node will run just behind the slow node

        Node prev = null;

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

        {

            prev = slow;

            //Next element of the list

            slow = slow.next;

            fast = fast.next.next;

        }

        prev.next = null;

    }

    public void displayContents()

    {

        //Iterate through ll

        //when we reach middle node, we assign its next reference to null

        //We will iterate through it with next pointer - as it is a custom linked list

        Node current = head;

        while(current!=null)

        {

            Console.Write(current.data +"->");

            //Next element of the list

            current = current.next;

        }

    }

    static void Main(string[] args)

    {

        CustomLinkedList ll = new CustomLinkedList();

        //Using Node Constructor

        Node firstNode = new Node(3);

        Node secondNode = new Node(4);

        Node thirdNode = new Node(5);

        Node fourthNode = new Node(6);

        //Assigning head and the following nodes in a linkedlist

        ll.head = firstNode;

        firstNode.next = secondNode;

        secondNode.next = thirdNode;

        thirdNode.next = fourthNode;

        ll.displayContents();

        ll.deleteBackHalf();

        Console.WriteLine();

        ll.displayContents();

    }

}