import Control.Monad

moveBot [x,y,l]
    | y >= 0 && x == 0  = (y + l - 1) `div` l
    | y >= 0 && x /= 0  = (y + l - 1) `div` l + ((abs x) + l - 1) `div` l + 1
    | otherwise         = ((abs y) + l - 1) `div` l + ((abs x) + l - 1) `div` l + 2

main = do
    xs <- map (read :: String -> Int) <$> replicateM 3 getLine
    print $ moveBot xs