import qualified Data.ByteString.Lazy.Char8 as C
import Data.Maybe (fromJust)

unsafeReadInt :: C.ByteString -> Int
unsafeReadInt = fst . fromJust . C.readInt

main :: IO ()
main = print . abs . sum .
    map (f . unsafeReadInt) . tail . C.words =<< C.getContents
        where f x = if odd x then -1 else 1