import Control.Applicative ((<$>))

main :: IO ()
main = solve <$> map read <$> words <$> getLine >>= print

solve :: [Int] -> Int
solve [x, y, d] | d < min x y = d + 1
                | d < max x y = min x y + 1
                | d <= x + y = x + y + 1 - d
                | otherwise = 0