#include <iostream>
#include <string>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <iomanip>

using namespace std;

#define REP(i, n) for(ll i = 0;i < n;i++)
#define REPR(i, n) for(ll i = n;i >= 0;i--)
#define FOR(i, m, n) for(ll i = m;i < n;i++)
#define FORR(i, m, n) for(ll i = m;i >= n;i--)
#define REPO(i, n) for(ll i = 1;i <= n;i++)
#define ll long long
#define INF (ll)1 << 60
#define MINF (-1 * INF)
#define ALL(n) n.begin(),n.end()
#define MOD 1000000007
#define P pair<ll, ll>


ll n, k, now = 0, know = INF, si[11000], ans;

int main() {
	cin >> n >> k;
	string s;
	cin >> s;
	REP(i, n) {
		if (i == k - 1) {
			if (s[i] == '(')know = now;
			else ans = si[now];
		}
		if (s[i] == '(') {
			now++;
			si[now] = i;
		}
		else now--;
		if (know == now) {
			ans = i;
			break;
		}
	}
	cout << ans + 1 << endl;
}