module Main (main) where

import qualified Data.ByteString.Char8 as C8
import qualified Data.Char as C
import qualified Data.List as L

main :: IO ()
main = readInts >>= print . solve

solve :: [Int] -> Int
solve [h,w]
  | h == 1 || w == 1 = 1
  | otherwise = uncurry (+) $ (h*w) `divMod` 2

-- utils
readInts :: IO [Int]
readInts = L.unfoldr (C8.readInt . C8.dropWhile C.isSpace) <$> C8.getLine