import java.util.Scanner;
    class Doublelinked
    {
     class Node 
     { 
       int data;
       Node next;
       Node back;
       Node(int d)
     {
      data=d;
     }
    }
    Node head=null;
    Node tail=null;
    void insertnode(int data)
    {
     Node newnode=new Node(data);
    if(head==null)
    {
     head=newnode;
     tail=newnode;
     head.back=null;
     tail.next=null;
    }
    else 
    {
     tail.next=newnode;
     newnode.back=tail;
     tail=newnode;
     tail.next=null;
     }
    }
    public void display()
    {
     Node current=head;
     if(head==null)
    {
     System.out.println("No Element");
    }
    else
    {
     while(current!=null)
    {    import java.util.Scanner;
    class Doublelinked
    {
     class Node 
     { 
       int data;
       Node next;
       Node back;
       Node(int d)
     {
      data=d;
     }
    }
    Node head=null;
    Node tail=null;
    void insertnode(int data)
    {
     Node newnode=new Node(data);
    if(head==null)
    {
     head=newnode;
     tail=newnode;
     head.back=null;
     tail.next=null;
    }
    else 
    {
     tail.next=newnode;
     newnode.back=tail;
     tail=newnode;
     tail.next=null;
     }
    }
    public void display()
    {
     Node current=head;
     if(head==null)
    {
     System.out.println("No Element");
    }
    else
    {
     while(current!=null)
    {
     System.out.print(""+current.data);
     current=current.next;
     }
    }}
    public void frontdelet()
    {
    try 
       {
        if(head==null)
    {
     System.out.println("No elements to delete");
    }
    head=head.next;
    if(head==null)
    {
     System.out.println("All Elements are deleted");
    }}
    catch(NullPointerException e)
    {
    }
    }}
    class Main
    {
    public static void main (String[]args)
    {
    Doublelinked d=new Doublelinked();
    int n,i,m,c;
     Scanner s=new Scanner(System.in);
    System.out.println("1.Insert node");
    System.out.println("2.Display");
    System.out.println("3.Deletion from Front");
    System.out.println("4 Deletion from back");
    while(5<10)
    {
     System.out.println("Enter Choice:");
    c= s.nextInt();
    switch(c)
    {
    case 1:System.out.println("Enter No:");
    m=s.nextInt();
    d.insertnode(m);
    break;
    case 2:d.display();
    break;
    case 3:d.frontdelet();
    break;
    default:System.out.println("Invalid key Sorry.");
    }
    }}}
     System.out.print(""+current.data);
     current=current.next;
     }
    }}
    public void frontdelet()
    {
    try 
       {
        if(head==null)
    {
     System.out.println("No elements to delete");
    }
    head=head.next;
    if(head==null)
    {
     System.out.println("All Elements are deleted");
    }}
    catch(NullPointerException e)
    {
    }
    }}
    class Main
    {
    public static void main (String[]args)
    {
    Doublelinked d=new Doublelinked();
    int n,i,m,c;
     Scanner s=new Scanner(System.in);
    System.out.println("1.Insert node");
    System.out.println("2.Display");
    System.out.println("3.Deletion from Front");
    System.out.println("4 Deletion from back");
    while(5<10)
    {
     System.out.println("Enter Choice:");
    c= s.nextInt();
    switch(c)
    {
    case 1:System.out.println("Enter No:");
    m=s.nextInt();
    d.insertnode(m);
    break;
    case 2:d.display();
    break;
    case 3:d.frontdelet();
    break;
    default:System.out.println("Invalid key Sorry.");
    }
    }}}