#include <bits/stdc++.h>

using namespace std;

template< typename key_t, typename val_t >
struct RadixHeap {
  static constexpr int bit = sizeof(key_t) * 8;
  array< vector< pair< key_t, val_t > >, bit > vs;

  size_t sz;
  key_t last;

  RadixHeap() : sz(0), last(0) {}

  bool empty() const { return sz == 0; }

  size_t size() const { return sz; }

  inline int getbit(int a) const {
    return a ? bit - __builtin_clz(a) : 0;
  }

  inline int getbit(int64_t a) const {
    return a ? bit - __builtin_clzll(a) : 0;
  }

  void push(const key_t &key, const val_t &val) {
    sz++;
    vs[getbit(key ^ last)].emplace_back(key, val);
  }

  pair< key_t, val_t > pop() {
    if(vs[0].empty()) {
      int idx = 1;
      while(vs[idx].empty()) idx++;
      last = min_element(vs[idx].begin(), vs[idx].end())->first;
      for(auto &p:vs[idx]) vs[getbit(p.first ^ last)].emplace_back(p);
      vs[idx].clear();
    }
    --sz;
    auto res = vs[0].back();
    vs[0].pop_back();
    return res;
  }
};


template< typename CapType, typename CostType >
class MinCostFlowDAG {
public:
  using Cat = CapType;
  using Cot = CostType;
  using pti = pair< Cot, int >;
  struct edge {
    int to, rev;
    Cat cap;
    Cot cost;
  };
  const int V;
  const Cot inf;
  vector< vector< edge > > G;
  vector< Cot > h, dist;
  vector< int > deg, ord, prevv, preve;

  MinCostFlowDAG(const int node_size) : V(node_size), inf(numeric_limits< Cot >::max()),
                                        G(V), h(V, inf), dist(V), deg(V, 0), prevv(V), preve(V) {}

  void add_edge(const int from, const int to, const Cat cap, const Cot cost) {
    if(cap == 0) return;
    G[from].push_back((edge) {to, (int) G[to].size(), cap, cost});
    G[to].push_back((edge) {from, (int) G[from].size() - 1, 0, -cost});
    ++deg[to];
  }

  bool tsort() {
    queue< int > que;
    for(int i = 0; i < V; ++i) {
      if(deg[i] == 0) que.push(i);
    }
    while(!que.empty()) {
      const int p = que.front();
      que.pop();
      ord.push_back(p);
      for(auto &e : G[p]) {
        if(e.cap > 0 && --deg[e.to] == 0) que.push(e.to);
      }
    }
    return (*max_element(deg.begin(), deg.end()) == 0);
  }

  void calc_potential(const int s) {
    h[s] = 0;
    for(const int v : ord) {
      if(h[v] == inf) continue;
      for(const edge &e : G[v]) {
        if(e.cap > 0) h[e.to] = min(h[e.to], h[v] + e.cost);
      }
    }
  }

  void Dijkstra(const int s) {
    RadixHeap< Cot, int > heap;
    fill(dist.begin(), dist.end(), inf);
    dist[s] = 0;
    heap.push(0, s);
    while(!heap.empty()) {
      pti p = heap.pop();
      const int v = p.second;
      if(dist[v] < p.first) continue;
      for(int i = 0; i < (int) G[v].size(); ++i) {
        edge &e = G[v][i];
        if(e.cap > 0 && dist[e.to] > dist[v] + e.cost + h[v] - h[e.to]) {
          dist[e.to] = dist[v] + e.cost + h[v] - h[e.to];
          prevv[e.to] = v, preve[e.to] = i;
          heap.push(dist[e.to], e.to);
        }
      }
    }
  }

  void update(const int s, const int t, Cat &f, Cot &res) {
    for(int i = 0; i < V; i++) {
      if(dist[i] != inf) h[i] += dist[i];
    }
    Cat d = f;
    for(int v = t; v != s; v = prevv[v]) {
      d = min(d, G[prevv[v]][preve[v]].cap);
    }
    f -= d;
    res += h[t] * d;
    for(int v = t; v != s; v = prevv[v]) {
      edge &e = G[prevv[v]][preve[v]];
      e.cap -= d;
      G[v][e.rev].cap += d;
    }
  }

  Cot solve(const int s, const int t, Cat f) {
    if(!tsort()) assert(false); // not DAG
    calc_potential(s);
    Cot res = 0;
    while(f > 0) {
      Dijkstra(s);
      if(dist[t] == inf) return -1;
      update(s, t, f, res);
    }
    return res;
  }
};


int main() {
  int N;
  cin >> N;
  string S;
  cin >> S;
  vector< int > V(N);
  for(auto &v : V) cin >> v;
  MinCostFlowDAG< int64_t, int64_t > flow(N + N + 2);
  int X = N + N;
  int Y = X + 1;
  string tmp = "yuki";
  for(int i = 0; i < N; i++) {
    flow.add_edge(2 * i, 2 * i + 1, 1, -V[i]);
    if(S[i] == 'i') {
      flow.add_edge(2 * i + 1, Y, 1, 0);
    } else {
      if(S[i] == 'y') {
        flow.add_edge(X, 2 * i, 1, 0);
      }
      int p = tmp.find(S[i]);
      for(int j = i + 1; j < N; j++) {
        if(tmp[p + 1] == S[j]) {
          flow.add_edge(2 * i + 1, 2 * j, 1, 0);
        }
      }
    }
  }
  flow.add_edge(X, Y, N / 4, 0);
  cout << -flow.solve(X, Y, N / 4) << "\n";
}