main = do
  [h, w] <- (map read) . words <$> getLine :: IO [Int]
  print $
    if w == 1 || h == 1
       then 1
    else
      if w `mod` 2 == 0
        then w`div`2 * h
      else
        if h `mod` 2 == 0
          then ((w`div`2)+1)*(h`div`2) + (w`div`2)*(h`div`2)
          else ((w`div`2)+1)*((h`div`2)+1) + (w`div`2)*(h`div`2)