import java.util.*;
import java.util.stream.Stream;
import java.time.*;
import java.time.format.*;

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);
    }
}