public static void Main()
Console.Write("Username :");
user = Console.ReadLine();
Console.Write("Password :");
pass = Console.ReadLine();
if(user!="admin" && pass!="a12345")
Console.Write("Username or password invalid! ! !");
Console.Write("Username invalid! ! !");
Console.Write("Password invalid! ! !");
Console.Write("Welcome! ! ! admin");