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

solve :: Integer -> Integer -> Integer -> Integer

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