import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int K = scan.nextInt();
		String S = scan.next();

		scan.close();
		Deque<Integer> stack = new ArrayDeque<Integer>();
		K--;
		for(int i = 0; i < N; i++) {
			char c = S.charAt(i);
			if(c == '(') {
				stack.push(i);
			}else {
				int k = stack.pop();
				if(i == K) {
					System.out.println(k + 1);
					break;
				}else if(k == K) {
					System.out.println(i + 1);
				}
			}
		}
	}
}