import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		final int N = sc.nextInt();
		final int K = sc.nextInt() - 1;
		
		final char[] S = sc.next().toCharArray();
		
		LinkedList<Integer> stack = new LinkedList<Integer>();
		for(int i = 0; i < N; i++){
			if(S[i] == '('){
				stack.push(i * (i == K ? -1 : 1));
			}else{
				final int value = stack.pop();
				
				if(value < 0){
					System.out.println(i + 1);
					return;
				}else if(i == K){
					System.out.println(value + 1);
					return;
				}
			}
		}
		
	}
	
}