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#include <bits/stdc++.h>
using namespace std;
constexpr int maxN = 1e5+7;

int n,k;
long long ans=1e18;
string s;

bool check(vector<char>essa, int l, int r){
    int ile = 0;
    for(int i=l;i<=r;i++){
        if(essa[i] == ')')
            ile--;
        else
            ile++;
        if(ile < 0)
            return false;
    }
    return (ile == 0);
}

long long cnt(vector<char>essa){
    long long res = 0;
    for(int i=0;i<essa.size();i++)
        for(int j=i;j<essa.size();j++)
            res += (int)check(essa,i,j);
    return res;
}

long long solve(int x){
    long long res = 0;
    vector<char>essa;
    for(int i=0;i<n-1;i++){
        essa.push_back(s[i]);
        if((1 << i) & x){
            res += cnt(essa);
            essa.clear();
        }
    }
    essa.push_back(s[n-1]);
    res += cnt(essa);
    return res;
}

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

    cin>>n>>k;
    cin>>s;
    for(int i=0;i<(1 << (n-1));i++){
        if(__builtin_popcount(i) != k-1)
            continue;
        ans = min(ans, solve(i));
    }
    cout<<ans<<"\n";
}
/*

15 2
())(()())()(())

*/