/**

 * Definition for singly-linked list.

 * public class ListNode {

 *     int val;

 *     ListNode next;

 *     ListNode(int x) { val = x; }

 * }

 */

class Solution {

    public ListNode deleteDuplicates(ListNode head) {

        if (head == null || head.next == null)return head;

        ListNode cur = head;

        while (cur.next != null) {

            if (cur.val == cur.next.val) {

                cur.next = cur.next.next;

            } else {

                cur = cur.next;

            }

        }

        return head;

    }

}