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#include <bits/stdc++.h>
using namespace std;
#define ff first
#define ss second


int n, k;
vector <int> v;
int last = -1;
string s;
int res = INT_MAX;

void count() {
	v.emplace_back(n);
	int l = 0;
	int wyn = 0;
	for (int i = 0; i < k; i++) {
		for (int j = l; j <= v[i]; j++) {
			int cur = 0;
			for (int a = j; a <= min(n-1, v[i]); a++) {
				if (s[a] == '(')
					cur++;
				else
					cur--;
				if (cur == 0) {
					wyn++;
				}
				if (cur < 0)
					break;
			}
		}
		l = v[i]+1;
	}
	res = min(res, wyn);
//	cout << wyn << "\n";
//	for (auto i : v)
//		cout << i << " ";
//	cout << "\n";
	v.pop_back();
}


void bt() {
	if ((int)v.size() == k-1) {
		count();
		return;
	}
	for (int i = last+1; i < n-1; i++) {
		int slast = last;
		last = i;
		v.emplace_back(i);
		bt();
		last = slast;
		v.pop_back();
	}
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cin >> n >> k;
	cin >> s;
	bt();
	cout << res << "\n";
}