using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        double num1;

        double num2;

        Console.WriteLine("Please input a number");

        while(!(double.TryParse(Console.ReadLine(), out num1)));

        Console.WriteLine("Please input a second number");

        while(!(double.TryParse(Console.ReadLine(), out num2)))

        Console.WriteLine("What operation");

        switch(char.ToUpper(userGrade))

        {

            case 'A':

                Console.WriteLine($"Excellent!");

                break;

            case 'B':

                Console.WriteLine($"Nice!");

                break;

            case 'C':

                Console.WriteLine("You'll get'em next time");

                break;

            case 'D':

                Console.WriteLine("Study harder!");

                break;

            case 'F':

                Console.WriteLine("What hell have though brought upon this wretched land? May thy crops be plagued by innumerable locusts, and thy waters be poisoned.");

                break;

            default:

                break;

        }

    }

}