package no022;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		String s = sc.next();
		int nest = 0;
		while(true) {
			if (s.charAt(k-1) == '(') {
				nest++;
			}else{
				nest--;
			}
			if (nest == 0) {
				break;
			}
			if (nest > 0) {
				k++;
			}else{
				k--;
			}
		}
		System.out.println(k);
	}

}