import qualified Data.ByteString.Char8 as BSC8
import qualified Data.Maybe            as Maybe

readIntegers :: IO [Integer]
readIntegers = map ( fst . Maybe.fromJust . BSC8.readInteger ) . BSC8.words <$> BSC8.getLine

solve :: Integer -> Integer
solve n
  | even n    = n `div` 2
  | otherwise = (n + 1) `div` 2
panasonicb :: IO ()
panasonicb = do
  (h:w:_) <- readIntegers
  print $ solve (h * w)