Console.WriteLine("Please enter the number (1-4)")
number = Console.ReadLine()
Loop Until number >= 1 AND number <= 4
Console.WriteLine("You listen to my command!")
Console.Writeline("Please enter the operator (A)dd, (S)ubtract, (M)ultiple, (D)ivide")
Do while op <> "A" AND op <> "S" AND op <> "M" AND op <> "D"
Console.Writeline("Please enter the operator (A)dd, (S)ubtract, (M)ultiple, (D)ivide")
Console.WriteLine("You listen to my command!")