q=3
username = "python"
userpassword = "123456"
while True:
    if q>0:
        name = input("请输入用户名:")
        password = input("请输入密码:")
        q-=1
        if name == username and password == userpassword:
            print("登录成功!")
            print("还有"+"str(q)"+"你就完蛋了！")
            break
        elif name!=username:
            print("用户名错误!请重新输入")
            print("还有"+"str(q)"+"你就完蛋了！")
        else:
            print("密码错误!请重新输入")
            exit               
print("欢迎来到贝尔编程!")