import Control.Applicative ((<$>))

getPair :: Int -> String -> Int
getPair k s
    | s !! (k - 1) == '(' = getPair' 0 k 1 s
    | otherwise           = getPair' 0 k (-1) s
    where
        getPair' n l d s
            | n == 0 && l /= k    = if d < 0 then l + 1 else l - 1
            | s !! (l - 1) == '(' = getPair' (n + 1) (l + d) d s
            | otherwise           = getPair' (n - 1) (l + d) d s

main :: IO ()
main = do
    (_ : k : _) <- map read . words <$> getLine
    s <- getLine
    print $ getPair k s