程序代码：

        

                 int id;
             cout << "请输入学生的id:";
            cin >> id;
        for (; id <= 0 && id <= 49;)
           {
                cout << "输入错误,请输入0-49之间" << endl;
                cout << "请重新输入学生id:";
                cin >> id;
            }
                cout<<id<<endl;