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