import java.util.Scanner;

public class Kakko {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();// 全体の数4
		int K = scan.nextInt();// 対象番号
		String S = scan.next();// かっこ
		int result = 0;

		if (S.charAt(K - 1) == '(') {
			int p = 0;
			for (int i = K - 1; i < N; i++) {
				if (S.charAt(i) == '(') {
					p++;
				} else {
					p--;
				}
				if (p == 0) {
					result = i;
					break;
				}
			}
		} else if (S.charAt(K - 1) == ')'){
			int p = 0;
			for (int i = K - 1; i < N; i--) {
				if (S.charAt(i) == '(') {
					p++;
				} else {
					p--;
				}
				if (p == 0) {
					result = i;
					break;
				}
			}
		}
		System.out.println(result+1);

	}

}