{-# LANGUAGE BangPatterns #-} import Control.Monad.State import Data.Char import Data.Coerce import Data.IORef import Data.Word import qualified Data.ByteString as BS import qualified Data.ByteString.Char8 as BSC8 import qualified Data.Vector.Fusion.Stream.Monadic as VFSM import qualified Data.Vector.Unboxed as VU main :: IO () main = do n <- readLn :: IO Int xs <- seqInput n a <- newIORef (0 :: Int) rep n $ \i -> if odd (xs VU.! i) then modifyIORef' a succ else modifyIORef' a pred print . abs =<< readIORef a stream :: Monad m => Int -> Int -> VFSM.Stream m Int stream !l !r = VFSM.Stream step l where step x | x < r = return $ VFSM.Yield x (x + 1) | otherwise = return $ VFSM.Done {-# INLINE [0] step #-} {-# INLINE [1] stream #-} rep :: Monad m => Int -> (Int -> m ()) -> m () rep n = flip VFSM.mapM_ (stream 0 n) {-# INLINE rep #-} type CParser a = StateT BSC8.ByteString Maybe a runCParser :: CParser a -> BSC8.ByteString -> Maybe (a, BSC8.ByteString) runCParser = runStateT {-# INLINE runCParser #-} int :: CParser Int int = coerce $ BSC8.readInt . BSC8.dropWhile isSpace {-# INLINE int #-} seqInput :: Int -> IO (VU.Vector Int) seqInput n = VU.unfoldrN n (runCParser int) <$> BSC8.getLine {-# INLINE seqInput #-}