import java.util.Scanner;

class Node {
    int data;
    Node prev, next;

    Node(int data) {
        this.data = data;
        prev = next = null;
    }
}

class DoublyLinkedList {
    Node head;

    void insert(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            newNode.next = head;
            head.prev = newNode;
            head = newNode;
        }
    }

    void delete(int data) {
        Node current = head;
        while (current != null) {
            if (current.data == data) {
                if (current.prev != null) {
                    current.prev.next = current.next;
                } else {
                    head = current.next;
                }

                if (current.next != null) {
                    current.next.prev = current.prev;
                }

                break;
            }
            current = current.next;
        }
    }

    void display() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
}

public class dll {
    public static void main(String[] args) {
        DoublyLinkedList list = new DoublyLinkedList();
        Scanner scanner = new Scanner(System.in);
        int choice, data;

        do {
            System.out.println("1. Insert");
            System.out.println("2. Delete");
            System.out.println("3. Display");
            System.out.println("4. Exit");
            System.out.print("Enter your choice: ");
            choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    System.out.print("Enter data to insert: ");
                    data = scanner.nextInt();
                    list.insert(data);
                    break;
                case 2:
                    System.out.print("Enter data to delete: ");
                    data = scanner.nextInt();
                    list.delete(data);
                    break;
                case 3:
                    System.out.print("Doubly Linked List: ");
                    list.display();
                    break;
                case 4:
                    System.out.println("Exiting program.");
                    break;
                default:
                    System.out.println("Invalid choice. Please enter a valid option.");
            }
        } while (choice != 4);
    }
}