main :: IO ()
main = interact $ show . solve . map read . words

myCeiling :: Int -> Int -> Int
myCeiling m n = ceiling $ (fromIntegral m) / (fromIntegral n)

solve :: [Int] -> Int
solve [x, y, l]
    | x /= 0 && y >= 0 = (myCeiling y l) + 1 + (myCeiling (abs x) l)
    | y < 0            = 1 + (myCeiling (abs x) l) + 1  + (myCeiling (abs y) l)
    | otherwise        = 0