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

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

	int ans;

	stack<int> paren_stack;
	for (int i = 0; i < s.length(); i++) {
		if (s[i] == '(') {
			paren_stack.push(i);
		}
		else {
			int pos = paren_stack.top(); paren_stack.pop();
			if (s[k - 1] == '(') {
				if (pos == k - 1) {
					ans = i + 1;
					break;
				}
			}
			else {
				if (i == k - 1) {
					ans = pos + 1;
					break;
				}
			}
		}
	}

	cout << ans << endl;

	return 0;
}