static void Main(string[] args)
Console.WriteLine(" DANG NHAP ");
Console.WriteLine("*****************************************************");
Console.Write(" Tai khoan: ");
Console.Write(" Mat khau: ");
if( tk== "CSKTLT" && mk == "fit@123" )
Console.Write(" DANG NHAP THANH CONG!");
Console.Write(" DANG NHAP THAT BAI!");