# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    def deleteDuplication(self, pHead):
        # write code here
        if not pHead or not pHead.next:
            return pHead 
        pre = ListNode(0)
        head = pre
        pre.next = pHead 
        cur = pHead 
        nxt = pHead.next 
        while nxt:
            if cur.val != nxt.val:
                if cur.next != nxt:
                    pre.next = nxt
                    cur = nxt
                else:
                    pre = pre.next 
                    cur = cur.next 
            nxt = nxt.next
        if cur.next:
            pre.next = None
        return head.next