#-*- coding: UTF-8 -*-
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def deleteDuplicates(self, head):
if head==None or head.next==None:return head
pre=head
cur=head.next
while cur!=None:
if pre.val!=cur.val:
pre=cur
cur=cur.next
continue
while cur.next!=None and cur.next.val==pre.val:
cur=cur.next
pre.next=cur.next
cur=pre.next
return head