#include<stdio.h>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <string>

using namespace std;

int main() {

	int N, K, ans;
	string S;
	cin >> N >> K >> S;

	/*
	stack<pair<int, int>> q;
	set<pair<int, int>> st;

	for (int i = 0; i < S.size(); i++) {
		if (S[i] == '(') {
			q.push(pair<int, int>(i+1, -1));
		}
		else {
			q.top().second = i + 1;
			st.insert(q.top());
			q.pop();
		}
	}

	set<pair<int, int>>::iterator it = st.begin();
	while (it != st.end()) {
		if (S[K - 1] == '(' && (*it).first == K) {
			ans = (*it).second;
			break;
		}
		else if(S[K - 1] == ')' && (*it).second == K){
			ans = (*it).first;
			break;
		}
		it++;
	}
	*/

	int d = 0, i;
	if (S[K-1] == '(') {
		for (i = K - 1; ;i++) {
			if (S[i] == '(') d++;
			else d--;
			if (d == 0) break;
		}
	}
	else {
		for (i = K - 1; ; i--) {
			if (S[i] == ')') d++;
			else d--;
			if (d == 0) break;
		}
	}

	cout << i+1 << endl;

	return 0;
}