import Data.Maybe (fromMaybe)

minNumOps :: Integral a => a -> a -> Maybe a
minNumOps x y
    | x == y = Just 0
    | y == 0 = Just 1
    | x == 0 = Just 2
    | x == -y = Just 3
    | otherwise = Nothing

main :: IO ()
main = do
    [x, y] <- fmap read . words <$> getLine :: IO [Int]
    print $ fromMaybe (-1) (minNumOps x y)