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 x = -1;
		int current = 0;
		if (arr[k - 1] == '(') {
    		for (int i = 0; i < n; i++) {
    		    if (i + 1 == k) {
    		        x = current;
    		    }
    		    if (arr[i] == '(') {
    		        current++;
    		    } else {
    		        current--;
    		    }
    		    if (current == x) {
    		        System.out.println(i + 1);
    		        return;
    		    }
    		}
		} else {
		    for (int i = n - 1; i >= 0; i--) {
    		    if (i + 1 == k) {
    		        x = current;
    		    }
    		    if (arr[i] == ')') {
    		        current++;
    		    } else {
    		        current--;
    		    }
    		    if (current == x) {
    		        System.out.println(i + 1);
    		        return;
    		    }
		    }
		}
   }
}