#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;
template<class T> bool chmin(T& a,T b){if(a>b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a,T b){if(a<b) {a = b; return true;} return false;}
#define rep(i,n) for(int i=0;i<(n);i++)
#define drep(i,n) for(int i=(n)-1;i>=0;i--)
#define all(x) (x).begin(),(x).end()
#define debug(x)  cerr << #x << " = " << (x) << endl;

using P = pair<ll,ll>;
const ll inf = 1e17;

class min_cost_flow{
private:
    int N;
    struct edge{int to; ll cap,cost; int rev; bool is_rev;};
    vector<vector<edge>> G;
    vector<ll> h,dist,prevv,preve;
public:
    min_cost_flow(int n){
        N = n;
        G = vector<vector<edge>>(N);
        h = dist = prevv = preve = vector<ll>(N,0);
    }
    void add_edge(int from,int to,ll cap,ll cost){
        G[from].push_back((edge){to,cap,cost,(int) G[to].size(),false});
        G[to].push_back((edge){from,0,-cost,(int) G[from].size()-1,true});
    }
    ll answer(int s,int t,ll f){
        ll res = 0;
        fill(h.begin(),h.end(),0);
        while(f>0){
            priority_queue<P,vector<P>,greater<P>> Q;
            fill(dist.begin(),dist.end(),inf);
            dist[s] = 0;
            Q.push(P(0,s));
            while(!Q.empty()){
                P p = Q.top(); Q.pop();
                int v = p.second;
                if(dist[v]<p.first) continue;
                for(int i=0;i<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;
                        Q.push(P(dist[e.to],e.to));
                    }
                }
            }
            if(dist[t]==inf) return -1;
            for(int v=0;v<N;v++) h[v] += dist[v];
            ll d = f;
            for(int v=t;v!=s; v=prevv[v]){
                d = min(d,G[prevv[v]][preve[v]].cap);
            }
            f -= d;
            res += d*h[t];
            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;
            }
        }
        return res;
    }
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    string S;
    cin >> S;
    vec<ll> A(N);
    rep(i,N) cin >> A[i];
    min_cost_flow flow(N+2);
    string yuki = "yuki";
    int s = N,t = N+1;
    ll offset = 1e15;
    rep(i,N){
        rep(j,4) if(S[i]==yuki[j]){
            if(j==0) flow.add_edge(s,i,1,0);
            if(j==3) flow.add_edge(i,t,1,offset-A[i]);
            for(int k=i+1;k<N;k++) if(S[k]==yuki[j]){
                flow.add_edge(i,k,inf,0);
                break;
            }
            if(j+1<4){
                for(int k=i+1;k<N;k++) if(S[k]==yuki[j+1]){
                    flow.add_edge(i,k,1,offset-A[i]);
                    break;
                }
            }
        }
    }
    flow.add_edge(s,t,inf,4*offset);
    cout << -(flow.answer(s,t,N)-4*N*offset) << "\n";
}