In reply to jackien:
Please use Code Tags. I have added them for you.
Did you read Section 6.19.4 Enumerated types in numerical expressions in the LRM? Did your code compile? Did you get a syntax error? Did your code run? Did your code give you a run-time error? Did your code work as expected? Did you get a different result than you expected?
It is difficult to provide assistance without additional information regarding the issue you are having.