main :: IO ()
main = do
  a <- readLn
  b <- readLn
  c <- readLn
  print $ solve (abs a) (abs b) c

solve :: Int -> Int -> Int -> Int

solve a b c = div (a + c - 1) c + d + div (b + c - 1) c
  where d = if a /= 0 then 1 else 0