public static void Main()
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))
Console.WriteLine($"Excellent!");
Console.WriteLine($"Nice!");
Console.WriteLine("You'll get'em next time");
Console.WriteLine("Study harder!");
Console.WriteLine("What hell have though brought upon this wretched land? May thy crops be plagued by innumerable locusts, and thy waters be poisoned.");