import java.util.*;

public class Run {
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int K = scan.nextInt() - 1;
        if (N < 1||N > 10000||K < 1||K > N) System.exit(1);
        String S = scan.next();
        if (S.length()!=N) System.exit(1);
        boolean flag;
        if (S.charAt(K)=='(') flag = true;
        else flag = false;
        Stack stackS = new Stack();
        int count = 0;
        if (flag) {
            while (true) {
                if (S.charAt(K) == '(') {
                    stackS.push(S.charAt(K));
                    count++;
                } else {
                    stackS.pop();
                    count--;
                    if (count==0) break;
                }
                K++;
            }
        } else {
            while (true) {
                if (S.charAt(K) == ')') {
                    stackS.push(S.charAt(K));
                    count++;
                } else {
                    stackS.pop();
                    count--;
                    if (count == 0) break;
                }
                K--;
            }
        }

        System.out.println(K+1);
    }
}