import Control.Monad

main = do
  [x,y,l] <- replicateM 3 readLn
  putStrLn . show $ (ceiling $ (abs x) / l) + (ceiling $ (abs y) / l) + (turnCnt x y)

turnCnt x y
  | x == 0 && y >= 0 = 0
  | x /= 0 && y >= 0 = 1
  | otherwise = 2