public static void Main()
Console.WriteLine("grade");
var grade= Console.ReadLine();
case "A":Console.WriteLine("Excellent");break;
case "B":Console.WriteLine("Well done");break;
case "C":Console.WriteLine("Well done");break;
case "D":Console.WriteLine("You passed");break;
case "F":Console.WriteLine("Better try again");break;
default:Console.WriteLine("Invalid grade");break;