import java.util.*;
 
// This program is used to detect if the linklist is circular or not.

class DetectCircularLinkList {
     
  static class Node {
      int data;
      Node next;
  }
 
/*This function returns true if given linked
list is circular, else false. */
  static boolean isCircular( Node head) {
      if (head == null)
      return true;

      Node node = head.next;
  
      while (node != null && node != head) {
        node = node.next;
      }
      return (node == head);
  }
 
  static Node newNode(int data) {
      Node temp = new Node();
      temp.data = data;
      temp.next = null;
      return temp;
  }

  public static void main(String args[]) {
      Node head = newNode(1);
      head.next = newNode(2);
      head.next.next = newNode(3);
      head.next.next.next = newNode(4);
  
      System.out.print(isCircular(head)? "Yes\n" :
                      "No\n" );
  

      head.next.next.next.next = head;
      System.out.print(isCircular(head)? "Yes\n" :
                      "No\n" );
  }
}