import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        String s = sc.next();
        sc.close();

        int count = 0;
        while (true) {
            if (s.charAt(k-1) == '(') count++;
            else count--;

            if (count > 0) k++;
            else if (count < 0) k--;
            else break;
        }

        System.out.println(k);
    }
}