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#include <bits/stdc++.h> //Michał Kuśmirek
using namespace std;     //XIII LO Szczecin

#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define REP(i, n) for(int i = 0; i < (n); ++i)

template<class T> int size(T && a) {
	return (int)(a.size());
}
ostream& operator << (ostream &os, string str) {
    for(char c : str) os << c;
    return os;
}
template <class A, class B> ostream& operator << (ostream &os, const pair<A, B> &p) {
	return os << '(' << p.first << "," << p.second << ')';
}
template <class T> auto operator << (ostream &os, T &&x) -> decltype(x.begin(), os) {
	os << '{';
	for(auto it = x.begin(); it != x.end(); ++it)
		os << *it << (it == prev(x.end()) ? "" : " ");
	return os << '}';
}
template <class T> ostream& operator << (ostream &os, vector<vector<T>> vec) {
    for(auto x : vec)
    	os << "\n  " << x;
    return os;
}
void dump() {}
template <class T, class... Args> void dump(T &&x, Args... args) {
    cerr << x << "; ";
    dump(args...);
}
#ifdef DEBUG
# define debug(x...) cerr << "[" #x "]: ", dump(x), cerr << '\n'
#else 
# define debug(...) 0
#endif

//--------------------------------------------------

bool correct(const string &s, int l, int r) {
	int balance = 0;
	FOR(i, l, r) {
		if(s[i] == '(')
			++balance;
		else --balance;

		if(balance < 0) return false;
	}

	return balance == 0;
}

int score(string &s, int l, int r) {
	int n = size(s);

	int answer = 0;
	FOR(i, l, r) FOR(j, i + 1, r) {
		answer += correct(s, i, j);
	}
	return answer;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	int n, k; 
	cin >> n >> k;
	string s; cin >> s;

	int answer = INT_MAX;
	REP(mask, (1 << (n - 1))) {
		if(__builtin_popcount(mask) != k - 1)
			continue;

		mask |= (1 << (n - 1));

		int ret = 0;
		int beg = 0;
		REP(i, n) if(mask & (1 << i)) {
			debug(beg, i);
			ret += score(s, beg, i);
			beg = i + 1;
		}

		mask ^= (1 << (n - 1));

		answer = min(answer, ret);
	}

	cout << answer << '\n';
}