import java.util.Scanner;


public class Main_yukicoder22 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        int k = sc.nextInt() - 1;
        char[] s = sc.next().toCharArray();
        
        if (s[k] == '(') {
        	int tmp = 0;
        	for (int i = k + 1; i < n; i++) {
        		if (s[i] == ')') {
        			if (tmp == 0) {
        				System.out.println(i + 1);
        				break;
        			} else {
        				tmp--;
        			}
        		} else {
        			tmp++;
        		}
        	}
        } else {
        	int tmp = 0;
        	for (int i = k - 1; i >= 0; i--) {
        		if (s[i] == '(') {
        			if (tmp == 0) {
        				System.out.println(i + 1);
        				break;
        			} else {
        				tmp--;
        			}
        		} else {
        			tmp++;
        		}
        	}
        }

        sc.close();
    }
}