import java.util.*;

public class Main {
    private static Scanner sc = new Scanner(System.in);
    public static void main(String[] args) throws Exception {
        int n = sc.nextInt();
        int k = sc.nextInt();
        String s = sc.next();
        Stack<Pair> stack = new Stack<>();
        for (int i = 1;i <= s.length();i++) {
            char c = s.charAt(i-1);
            Pair p;
            if (c=='(') {
                stack.push(new Pair(i==k,i));
            } else {
                p = stack.pop();
                if (i==k) {
                    System.out.println(p.c);
                    return;
                } else if (p.b) {
                    System.out.println(i);
                    return;
                }
            }
        }
    }
    
    static class Pair {
        boolean b;
        int c;
        public Pair(boolean b, int c) {
            this.b = b;
            this.c = c;
        }
    }
}