solve :: Int -> Int -> Int
solve h w
 | (h > 1) && (w > 1) = ((div (h + 1) 2) * (div (w + 1) 2)) + ((div h 2) * (div w 2))
 | otherwise = 1

main :: IO()
main = do
 [h,w] <- map read . words <$> getLine :: IO [Int]
 print $ solve h w