(defun main (&rest argv)
  (declare (ignorable argv))
  (let* ((n (read))
         (k (1- (read)))
         (s (read-line))
         (c (aref s k))
         (a 0))
    (declare (ignore n))
    (loop while (>= a 0) do
          (incf k (if (eql c #\() 1 -1))
          (incf a (if (eql c (aref s k)) 1 -1)))
    (format t "~d~%" (+ k 1))))

(main)