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

using namespace std;

int N, K;
string S;

int main() {
	cin >> N >> K;
	K--;
	cin >> S;
	stack<int> stack;
	for (int i = 0; i < S.length(); i++) {
		if (S[i] == '(') {
			stack.push(i);
		} else {
			int f = stack.top();
			stack.pop();
			if (f == K) {
				cout << (i + 1) << endl;
				break;
			} else if (i == K) {
				cout << (f + 1) << endl;
				break;
			}
		}
	}
	return 0;
}