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

int main() {
	int n, k;
	string s;
	cin >> n >> k >> s;

	int ans;

	if (s[k - 1] == '(') {
		int pos = k;
		for (int i = k; i < s.length(); i++) {
			if (s[i] == '(')
				pos++;
			else
				pos--;
			if (pos == k - 1)
				ans = i + 1;
		}
	}
	else {
		int pos = k - 2;
		for (int i = k - 2; i >= 0; i--) {
			if (s[i] == '(')
				pos++;
			else
				pos--;
			if (pos == k - 1)
				ans = i + 1;
		}
	}

	cout << ans << endl;

	return 0;
}