import Control.Applicative
import Control.Monad
import Data.List
import Data.Monoid

divCeil x y = (x + y - 1) `div` y

f :: Int -> Int -> Int -> Int
f x y l
  | y>=0 && x==0 = divCeil y l
  | y>=0 = divCeil y l + 1 + divCeil (abs x) l
  | otherwise = 1 + divCeil (abs x) l + 1 + divCeil (abs y) l

main = f <$> readLn <*> readLn <*> readLn >>= print