#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	int N, K;
	string S;
	cin >> N >> K >> S;
	int cnt  = 0;
	int kcnt = -10001;
	K--;
	bool revFlag = S[K] == ')';
	for (int i = 0; i < S.size(); i++) {
		int index		   = i;
		if (revFlag) index = N - 1 - i;
		char c			   = S[index];
		if (cnt + (c == '(' ? 1 : -1) == kcnt) {
			cout << index + 1 << endl;
			return 0;
		}
		if (index == K) {
			kcnt = cnt;
		}
		cnt += c == '(' ? 1 : -1;
	}
	return 0;
}