import Data.Array

solve :: Int -> Array Int Char -> Int
solve k a
  | a!k == '(' = right (k+1) 1 - 1
  | a!k == ')' = left  (k-1) 1 + 1
  | otherwise = undefined
  where
    right i 0 = i
    right i c
      | a!i == '(' = right (i+1) (c+1)
      | a!i == ')' = right (i+1) (c-1)
      | otherwise = undefined
    left i 0 = i
    left i c
      | a!i == ')' = left (i-1) (c+1)
      | a!i == '(' = left (i-1) (c-1)
      | otherwise = undefined

main :: IO ()
main = do
    [n,k] <- map read . words <$> getLine :: IO [Int]
    s <- getLine :: IO String
    let a = listArray (1,n) s :: Array Int Char
    print $ solve k a