import Control.Applicative ((<$>), (<*>))
import Control.Monad
import Data.List

main :: IO ()
main = do
  solve <$> getl read <*> getl read <*> getl read >>= print

solve :: Int -> Int -> Int -> Int
solve x y l | x == 0 && y == 0 = 0
            | y >= 0 && x == 0 = yp
            | y >= 0 = 1 + xp + yp
            | otherwise = 2 + xp + yp
  where
    xp = (abs x + l - 1) `div` l
    yp = (abs y + l - 1) `div` l

getl :: (String -> a) -> IO a
getl f = f <$> getLine