#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
#define rep(i,a,b) for(int i = a; i < (b); i++)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define PB push_back
#define FS first
#define SD second
#define cmx(x, y) x = max(x, y)
#define cmn(x, y) x = min(x, y)
#define ary(k) array<int, k>
typedef pair<int, int> pii;
typedef vector<int> vi;

int cost[1000002];
int change[1000002];

int suf(int a) {
//    cerr << a << " ";
    int rj = 1;
    if (a < 0) {
        rj = -1;
        a *= -1;
    }
//    cerr << rj*((a+1)/2) << "suf\n";
    return rj*((a+1)/2);
}

signed main() {
    cin.tie(0)->sync_with_stdio(0); cin.exceptions(cin.failbit);
    int n, k;
    cin >> n >> k;
    string slo;
    cin >> slo;
    int pocz_min = 0;
    set<pii> pq;
    set<pii, greater<pii>> used;
    for (int i = 0; i < n; i++) {
        cin >> cost[i];
        if (cost[i] < 0) {
            pocz_min -= cost[i];
            cost[i] *= -1;
            if (slo[i] == ')')
                slo[i] = '(';
            else
                slo[i] = ')';
        }
        if (slo[i] == ')')
            pq.insert({cost[i], i});
    }
    if (n%2) {
        cout << -pocz_min << "\n";
        return 0;
    }
//    if (2*k >= n) {
//        cout << "?\n";
//        return 0;
//    }
    int k1 = 0, k2 = 0;
    for (int i = 0; i < n; i++) {
        if (slo[i] == ')') {
            k2--;
        } else {
            k2++;
        }
        cmx(k1, -k2);
    }
    int best = 1e18;
    int akt = 0, curst = 0, curcost = 0, kk = 0;
    while (!pq.empty() && curst + k2/2 <= k) {
        auto [c, id] = *pq.begin();
        pq.erase({c, id});
        used.insert({c, id});
        curst++;
        curcost += c;
        change[id] = 1;
    }
    if (curst + k2/2 > k)
        cmn(best, curcost);
//    cerr << best << "\n";
//    cerr << k2 << "\n";
    for (int i = 0; i < n; i++) {
        if (slo[i] == ')') {
            akt++;
        } else {
            akt--;
        }
        cmx(kk, akt);
        if (change[i] == 1) {
            curst--;
            curcost -= cost[i];
            used.erase({cost[i], i});
            change[i] = 0;
        } else if (slo[i] == ')') { // TODO: Tu weszła zmiana
            pq.erase({cost[i], i});
        }
        if (slo[i] == '(') {
            pq.insert({cost[i], i});
        }
//        cerr << curst << "c1 " << curcost << "\n";
        int have = k2/2 + suf(akt) * 2;
        while (have + curst > k + 1 && used.size() > 0) {
            auto [c, id] = *used.begin();
            curst--;
            curcost -= c;
            used.erase({c, id});
            change[id] = 0;
            pq.insert({c, id});
        }
        while (!pq.empty() && !used.empty()) {
            auto [c1, id1] = *used.begin();
            auto [c2, id2] = *pq.begin();
            if (c1 > c2) {
                used.insert({c2, id2});
                used.erase({c1, id1});
                pq.erase({c2, id2});
                pq.insert({c1, id1});
                curcost += (c2-c1);
                change[id1] = 0;
                change[id2] = 1;
            } else {
                break;
            }
        }
//        cerr << curst << "c2 " << curcost << "   ";
//        cerr << i << " " << have << "   ";
        while (!pq.empty() && curst + have <= k) {
            auto [c, id] = *pq.begin();
            pq.erase({c, id});
            used.insert({c, id});
            curst++;
            curcost += c;
            change[id] = 1;
        }
        if (have + curst > k)
            cmn(best, curcost);
//        cerr << curcost << "\n";
    }
    if (best > 1e17)
        cout << "?\n";
    else
        cout << best - pocz_min << "\n";

}