import java.util.*;

class node {
    int data;
    node next;
    node prev;

    static void insert(node start, int data)
    {
        node newNode = new node();
        newNode.data = data;

        if(start==null) {
            newNode.next=newNode.prev=null;
            start = newNode;
        } else {
            node t = start;
            while(t.next!=null)
            t = t.next;
            newNode.prev = t;
            t.next = newNode;
            newNode.next=null;
        }
    }

    static void delete(node start, int data) {
        node t = start;
        try {
            while(t.data!=data)
                t = t.next;
        t.prev.next = t.next;
        t.next.prev = t.prev;
        } catch (NullPointerException e) {
            System.out.println("Data NOT found!");
        }
    }

    static void traverse(node start) {
        node t = start;
        while(t!=null) {
            System.out.println(t.data);
            t=t.next;
        }
    }
}

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        node start=null;

        int ch=0;
        while(ch!=4)
        {
            System.out.println("n1. Insert Node");
            System.out.println("2. Delete Node");
            System.out.println("3. Print nodes");
            System.out.println("4. Exit!");
            System.out.print("Enter Your Choice: ");

            ch = sc.nextInt();

            switch(ch)
            {
                case 1: System.out.print("nEnter the value of the node to insert: ");
                        int val = sc.nextInt();
                        node.insert(start, val);
                        System.out.println("DEBUG   :   Start val: "+start.data);
                        break;
                case 2: System.out.print("nEnter the value of the node you want to delete: ");
                        node.delete(start, sc.nextInt());
                        break;
                case 3: node.traverse(start);
                        break;
                case 4: System.out.println("nBye!!");
                        break;
                default:    System.out.println("nWrong value: Please try again!");
            }
        }
    }
}