FUNCTION Double(n)
   RETURN n * 2

FUNCTION Add(a, b)
   RETURN a + b

FUNCTION Main()
   LOCAL result

   result := Double(21)
   ? "Double(21) =", result

   result := Add(10, 20)
   ? "Add(10,20) =", result

   result := Double(Add(3, 4))
   ? "Double(Add(3,4)) =", result

   ? "Done!"
   RETURN NIL