#include <iostream>
#include <string>
using namespace std;
int main() {
	int l = 0, r = 0;
	int N, K;
	string S;
	cin >> N >> K;
	cin >> S;
	if (S[K - 1] == '(') {
		for (int i = K - 1; i < N;i++) {
			if (S[i] == '(') { l++; }
			if (S[i] == ')') { r++; }
			if (l == r) { cout << i + 1 << endl; return 0; }
		}
	}
	else {
		for (int i = K - 1; i >= 0;i--) {
			if (S[i] == '(') { l++; }
			if (S[i] == ')') { r++; }
			if (l == r) { cout << i + 1 << endl; return 0; }
		}
	}
	return 0;
}