pB :: Int -> [Int] -> [(Char, Int)] -> Int
pB k ns ((b,n'):bs) =
  if b == '(' then
    pB k (n':ns) bs
  else
    case ns of
      [] -> 0
      (n:ns') ->
        if n == k then n'
        else if n' == k then n
        else pB k ns' bs

main = do
  [n,k] <- (map read . words) <$> getLine
  s <- getLine
  putStrLn $ show $ pB k [] $ zip s [1..]