using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("請輸入使用者名稱:");

        string username, password;

        username=Console.ReadLine();

        if ( username =="馬壯")

        {

            Console.WriteLine(username+"您好");

        }

        else if (username == "徐強")

        {

            Console.WriteLine(username+"您好");

        }

        else

        {

            Console.WriteLine("本系統不認識"+username);

        }

            Console.Write(username+"請輸入密碼:");

            password = Console.ReadLine();

            if ( (password == "egg566") ||

                (password == "EGG566"))

            {

                Console.WriteLine("歡迎進入本系統");

            }

        else if (username == "徐強")

        {

            if ( (password == "dog123") ||

            (password == "DOG123") );

            Console.WriteLine("歡迎進入本系統");

            else

            {

                Console.WriteLine("密碼錯誤");

            }

            }

        else

        {

                Console.WriteLine("密碼錯誤");

        }

​