import Monad (MonadPlus(..), liftM, liftM2, when)
import Char (isAlpha, isAlphaNum, isSpace, isDigit, toUpper, intToDigit, ord)
import List (intersperse, isSuffixOf)
import Monad (MonadPlus(..), liftM, liftM2, when)
import Char (isAlpha, isAlphaNum, isSpace, isDigit, toUpper, intToDigit, ord)
import List (intersperse, isSuffixOf)