import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		char[] arr = sc.next().toCharArray();
		int count = 0;
		if (arr[k - 1] == '(') {
		    for (int i = k - 1; ; i++) {
		        if (arr[i] == '(') {
		            count++;
		        } else {
		            count--;
		        }
		        if (count == 0) {
		            System.out.println(i + 1);
		            return;
		        }
		    }
		} else {
		    for (int i = k - 1; ; i--) {
		        if (arr[i] == '(') {
		            count++;
		        } else {
		            count--;
		        }
		        if (count == 0) {
		            System.out.println(i + 1);
		            return;
		        }
		    }
		}
	}
}