solve :: Int -> Int -> Int -> Int
solve x y l = (d + l - 1) `div` l + t
  where
    t = if y < 0 then 1 else 0 +
        if x /= 0 then 1 else 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