#include <iostream>
#include <string>
using namespace std;

int main(void) {
    int N, K;
    string S;
    cin >> N >> K >> S;
    int dan = 0;
    int kdan;
    if (S[K - 1] == '(') {
        for (int i = K; i < N; i++) {
            if (S[i] == '(') {
                dan++;
            } else {
                dan--;
            }
            if (dan == -1) {
                cout << i + 1 << endl;
                break;
            }
        }
    } else {
        for (int i = K - 2; i >= 0; i--) {
            if (S[i] == '(') {
                dan++;
            } else {
                dan--;
            }
            if (dan == 1) {
                cout << i + 1 << endl;
                break;
            }
        }
    }

    return 0;
}