import Control.Monad
import Data.List

main = do
  [n, k] <- map read . words <$> getLine :: IO [Int]
  s <- getLine
  
  let x = s !! (k - 1)
  let s' = if x == '(' then drop k s else take (k - 1) s
  let result = if x == '(' then checkL s' 0 0 else checkR (reverse s') 0 0
  
  putStrLn . show $ if x == '(' then result + k else (length s') - result + 1
  
checkL (c:cs) count no
  | c == '(' = checkL cs (count + 1) (no + 1)
  | c == ')' && count > 0 = checkL cs (count - 1) (no + 1)
  | otherwise = no + 1

checkR (c:cs) count no
  | c == ')' = checkR cs (count + 1) (no + 1)
  | c == '(' && count > 0 = checkR cs (count - 1) (no + 1)
  | otherwise = no + 1