main = do
  x <- fmap read getLine :: IO Int
  y <- fmap read getLine :: IO Int
  l <- fmap read getLine :: IO Int
  let
    t = if y < 0 then 2 else if x == 0 then 0 else 1
    lx = div (abs x - 1) l + 1
    ly = div (abs y - 1) l + 1
  putStrLn $ show $ lx + ly + t