/**
 * Simple Singly-linked-list node.
 */
public class ListNode {

  public int val;
  public ListNode next;

  public ListNode(int val, ListNode next) {
    this.val = val;
    this.next = next;
  }

  public ListNode(int val) {
    this.val = val;
    this.next = null;
  }

  public ListNode() {
    this.val = 0;
    this.next = null;
  }
}