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

using namespace std;

int main()
{
	int N, K;
	string S;
	cin >> N >> K >> S;
	--K;

	if (S[K] == '(') {
		int open = 0;
		for (int i = K; i < N; ++i) {
			if (S[i] == '(') {
				++open;
			} else {
				--open;
			}
			if (open == 0) {
				cout << i + 1 << endl;
				break;
			}
		}
	} else {
		int close = 0;
		for (int i = K; i >= 0; --i) {
			if (S[i] == ')') {
				++close;
			} else {
				--close;
			}
			if (close == 0) {
				cout << i + 1 << endl;
				break;
			}
		}
	}
}