# -*- 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

        if pHead.val == pHead.next.val:

            temp = pHead.next

            while temp and temp.val == pHead.val:

                temp = temp.next

            return self.deleteDuplication(temp)

        else:

            pHead.next = self.deleteDuplication(pHead.next)

            return pHead

class Solution:

    def deleteDuplicates(self, head: ListNode) -> ListNode:

        thead = ListNode('a')

        thead.next = head

        pre,cur = None,thead

        while cur:

            pre=cur

            cur=cur.next

            while cur and cur.next and cur.next.val == cur.val:

                t=cur.val

                while cur and cur.val==t:

                    cur=cur.next

            pre.next=cur

        return thead.next