说明：  设计一个登陆系统，该系统有管理员和学生两个角色。学生可以从命令行输入姓名和密码进行登陆，登陆失败应有相应的提示信息。学生登陆之后显示自己的信息，也可以查看其他所有学生的信息。输入退出命令之后，返回登陆界面，输入管理员用户名和密码，登陆成功之后即显示所有学生信息，可以选择新增或删除选项，分别新增或删除学生。
(Design a landing system, which has two roles administrators and students. Students can enter a name and password to log in from the command line, login failures should be a corresponding message. Students display their information after landing, you can see all the other student information. After you enter the exit command to return to the login screen, enter the administrator user name and password, after the successful landing of all student information is displayed, you can choose to add or delete options, respectively, add or delete students.)