import Control.Applicative ((<$>), (<*>))

main :: IO ()
main = do
  solve <$> getl (map read . words) <*> getLine >>= print

solve :: [Int] -> String -> Int
solve [n, k] s = f 1 [] s
  where
    f i st (c:cs) = if c == '(' then f (i + 1) (i : st) cs
                    else if head st == k then i
                         else if i == k then head st
                              else f (i + 1) (tail st) cs

getl :: (String -> a) -> IO a
getl f = f <$> getLine