#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <iomanip>
#include <functional>
#include <cmath>
using namespace std;

int main() {
	int n, k, x = 0;
	string str;
	cin >> n >> k >> str;
	if (k > n / 2) {
		reverse(str.begin(), str.end());
		k = n - k;
	}
	for (int i = k; i < n; i++) {
		if (str[i] == '(') x++;
		else if (x == 0) {
			cout << i + 1<< endl;;
			return 0;
		}
		else x--;
	}
	return 0;
}