import java.util.Scanner;

public class Yukicoder22 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt() - 1;
		String s = sc.next();

		int i = 0, count = 0;
		if (s.charAt(k) == '(') {
			for (i = k + 1; i < s.length(); i++) {
				if (s.charAt(i) == '(') {
					count++;
				} else if (s.charAt(i) == ')') {
					if (count == 0) break;
					count--;
				}
			}
		} else if (s.charAt(k) == ')') {
			for (i = k - 1; i >= 0; i--) {
				if (s.charAt(i) == '(') {
					if (count == 0) break;
					count++;
				} else if (s.charAt(i) == ')') {
					count--;
				}
			}
		}
		System.out.println(i + 1);
	}
}