ATM机:假设一个简单的ATM的取款过程是这样的：首先提示用户输入密码，最多只能输3次，超过三次则提示用户“密码错误，请取卡。“结束交易。-ATM machine: withdrawal process assuming a simple ATM is this: first, prompt the user to enter a password, most can only lose 3 times, more than three times the user is prompted to