Huiaskel additional 1-7

import Control.Monad
import qualified Data.ByteString.Char8 as B
import Data.Maybe
import Data.List
import Control.Arrow

readInt :: B.ByteString -> Int
readInt = fst . fromJust . B.readInt

main :: IO ()
main = do
  [len] <- liftM (map readInt . B.words) B.getLine
  lst   <- liftM (map readInt . take len . B.words) B.getLine :: IO [Int]
  putStrLn "Input: "
  print lst
  putStrLn "Result: "
  print (count_distinct lst)

count_distinct_impl []    _   ans = ans
count_distinct_impl (h:t) cur ans | h == cur  = count_distinct_impl t h ans
                         | otherwise = count_distinct_impl t h (ans + 1)

count_distinct []  = 0
count_distinct lst = count_distinct_impl (tail sorted) (head sorted) 1
        where sorted = sort lst

--5
--3 -1 2 4 2