#!/usr/bin/env python
# -*- coding: utf-8 -*-
count = 0
for i in range(3):#循环三次终止输入
    user = input ('Please input your name: ')
    pwd = input('Please input your password: ')
    if user == 'liuchao' and pwd == '123456':
        print ('Welcome to Beijing')
        break #输入正确的用户名和密码显示欢迎信息并结束
    else :
        if count < 2 : #第三次输入错误后打印锁定提示不再显示再出输入
            print ('please again') #提示再次输入
            count +=1
else :
    print ('You are not allowed to enter !!!') #锁定提示