# -*- coding:utf-8 -*-

class ListNode:

def __init__(self, x):

self.val = x

self.next = None

class Solution:

def ReverseList(self, pHead):  
    if pHead is None:  
        return  
    last=None  
    while pHead is not None:  
        tmp=pHead.next  
        pHead.next=last  
        last=pHead  
        pHead=tmp

    return last