solve :: Int -> Int -> Int -> Int
solve x y l = (d + l - 1) `div` l + t
  where
    t | y < 0 = 2
      | x /= 0 = 1
      | otherwise = 0
    d = abs x + abs y

main :: IO ()
main = do
    x <- readLn :: IO Int
    y <- readLn :: IO Int
    l <- readLn :: IO Int
    print $ solve x y l