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username = "python"
userpassword = "123456"
while True:
    name = input("请输入用户名")
    password = input("请输入密码")
    if name ==username and password ==userpassword：
       print("登陆成功")
       break
    if name!=username:   
       print("用户名错误！请重新输入")
       cintinue
    if password!=userpassword：
print("欢迎来到贝尔编程")