1 abstract class RomanDigit 

     2 case object I extends RomanDigit 

     3 case object V extends RomanDigit 

     4 case object X extends RomanDigit 

     5 case object L extends RomanDigit 

     6 case object C extends RomanDigit 

     7 case object D extends RomanDigit 

     8 case object M extends RomanDigit