main = do
  [h,w] <- map read . words <$> getLine :: IO [Int]
  let ho = (h `div` 2) + (h `mod` 2)
  let he = h `div` 2
  let wo = w `div` 2 + (w `mod` 2)
  let we = w `div` 2 
  print $ (ho * wo) + (he * we)
