当用户的次数超过三次时，提示是否还要继续？输入为N，或者为n就退出系统，否则继续。

#!/usr/bin/env python
# _*_ coding:utf8 _*_
#author:snate
cnt=0;
alex_age=50
while cnt<3:
   guess_age =int(input("请输入您猜测的年龄："))
   if alex_age==guess_age:
      print("You are lucky,you got it");
      break
   elif alex_age>guess_age:
      print("Think bigger");
   else:
      print("think smaller");
   cnt += 1
   if cnt==3:
      continue_flag = input("do you want continue?(yes or no)")
      if continue_flag !="n":
         cnt=0
      else:
         print("提出系统！\n")
         break