import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		try (Scanner scan = new Scanner(System.in)) {
			int N = scan.nextInt();
			int K = scan.nextInt();
			char S[] = scan.next().toCharArray();
			
			int count = 0;
			if(S[K-1] == '(') {
				for(int i=K-1; i<N; i++) {
					if(S[i] == '(') {
						count++;
					} else  {
						count--;
						if(count == 0) {
							System.out.println(i+1);
							break;
						}
					}
				}
			} else {
				for(int i=K-1; i>=0; i--) {
					if(S[i] == ')') {
						count++;
					} else  {
						count--;
						if(count == 0) {
							System.out.println(i+1);
							break;
						}
					}
				}
			}
		}
	}
}