import Control.Applicative ((<$>))

solve :: Int -> Int -> Int -> Int
solve a b s
    | s == 1 || da < db = s + abs (s - a)
    | a == 0            = ans + 2
    | otherwise         = ans
    where
        da = abs (a - s)
        db = abs (b - s)
        ans = a + db + min da (s - 1)

main :: IO ()
main = do
    [a, b, s] <- map read . words <$> getLine
    print $ solve a b s