class Node{
    int data;
    Node prev;
    Node next;

    public Node(int data){
        this.data = data;
    }

    public void tampil(){
        System.out.println("{"+data+"}");
    }
}

public class CircularLL {
    Node first;
    Node last;
    int size;

    public CircularLL(){
        first = null;
        last  = null;
    }

    public boolean isEmpty(){
        return(first==null);
    }

    public void insertFirst(int data){
        Node node = new Node(data);
        if(isEmpty()){
            last = node;
            first = node;
        }else{
            node.next = first;
            first.prev = node;
        }
        first = node;
        first.prev = last;
        last.next = first;
        size++;
    }

    public void insertLast(int data){
        Node node = new Node(data);
        if(isEmpty()){
            last = node;
            first = node;
        }else{
            node.prev = last;
            last.next = node;
        }
        last = node;
        first.prev = last;
        last.next = first;
        size++;
    }

    public void displayForward(){
        System.out.println("List (first-->last): "+size);
        Node current = first;
        int no =1;
        while(no <= size){
            current.tampil();
            current = current.next;
            no++;
        }
        System.out.println("");
    }

    public void displayBackward(){
        System.out.println("List (last-->first): "+size);
        Node current = last;
        int no =1;
        while(no <= size){
            current.tampil();
            current = current.prev;
            no++;
        }
        System.out.println("");
    }

    public Node deleteFirst(){
        Node temp = first;
        if(first.next == null){
            last = null;
        }else{
            first.next.prev = last;
            first = first.next;
            last.next = first;
        }
        size--;
        return temp;
    }

    public Node deleteLast(){
        Node temp = last;
        if(first.next == null){
            last = null;
        }else{
            last.prev.next = first;
            last = last.prev;
            first.prev = last;
        }
        size--;
        return temp;
    }

    public Node deleteKey(int key){
        Node current = first;
        while(current.data != key){
            current = current.next;
        }
        if(current==first){
            current = deleteFirst();
        }else if(current==last){
            current = deleteLast();
        }else{
            current.next.prev = current.prev;
            current.prev.next = current.next;
        }
        size--;
        return current;
    }

    public void display(){
        Node current = last.prev;

        current.tampil();
        System.out.println("");
    }

    public boolean insertAfter(int key, int data){
        Node current = first;
        while(current.data != key){
            current = current.next;
        }
        Node node = new Node(data);

        if(current==last){
            insertLast(data);
        }else{
            current.next.prev = node;
            node.next = current.next;
            node.prev = current;
            current.next = node;
            size++;
        }
        return true;
    }

    public static void main(String[] args){
        CircularLL list = new CircularLL();
        list.insertFirst(1);
        list.insertFirst(2);
        list.insertFirst(3);
        list.insertFirst(4);
        list.insertLast(0);
        list.insertLast(5);
        list.displayForward();
        list.deleteLast();
        list.displayForward();
        list.deleteKey(55);
        list.insertAfter(5,10);
        list.displayForward();
    }


}