#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;

int main() {
	int n, k;
	string str;

	cin >> n >> k >> str;
	k--;

	int pile = 0;

	int ans;
	if (str[k] == '(') {
		for (int i = k; i < n; i++) {
			if (str[i] == '(') {
				pile++;
			} else {
				pile--;
				if (pile == 0) {
					ans = i + 1;
					break;
				}
			}
		}
	} else {
		for (int i = k; i >= 0; i--) {
			if (str[i] == ')') {
				pile++;
			} else {
				pile--;
				if (pile == 0) {
					ans = i + 1;
					break;
				}
			}
		}
	}
	cout << ans << endl;
	return 0;
}