#include<iostream>
#include<stack>
#include<algorithm>
#include<string>

int main() {
	int n, k;
	std::string str;
	std::stack<int> s;
	std::cin >> n >> k >> str;

	for (int i = 0; i < str.length(); i++) {
		if (str[i] == '(') {
			s.push(i);
		} else {
			if (i + 1 == k) {
				std::cout << s.top() + 1 << std::endl;
				break;
			} else if (s.top() + 1 == k) {
				std::cout << i + 1 << std::endl;
				break;
			}
			s.pop();
		}
	}
	return 0;
}