import java.util.Scanner;

public class No22 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int K = sc.nextInt();
		String S = sc.next();
		String str[] = S.split("");
		int count = 0;
		int i = K - 1;
		while(true) {
			if(str[i].equals("(")){
				count++;
			}else {
				count--;
			}
			
			if(count == 0) {
				break;
			}
			
			if(str[K - 1].equals("(")) {
				i++;
			}else {
				i--;
			}
		}
		
		System.out.println(i + 1);
	}
}