#include<iostream>
using namespace std;
//Minimum Cost Flow O(FE log V)
#include<algorithm>
#include<utility>
#include<vector>
#include<queue>
#include<limits>
template<typename T>
struct MCF{
	struct edge{
		int to,rev,cap;
		T cost;
	};
	vector<vector<edge> >G;
	vector<T>h,d;
	vector<int>pv,pe;
	MCF(int n_=0):G(n_),h(n_,0),d(n_),pv(n_),pe(n_){}
	void add_edge(int from,int to,int cap,T cost)
	{
		G[from].push_back({to,(int)G[to].size(),cap,cost});
		G[to].push_back({from,(int)G[from].size()-1,0,-cost});
	}
	T min_cost_flow(int s,int t,int f)//ans or -1
	{
		T ret=0;
		while(f>0)
		{
			queue<pair<T,int> >P;
			fill(d.begin(),d.end(),numeric_limits<T>::max());
			d[s]=0;
			P.push(make_pair(0,s));
			while(!P.empty())
			{
				pair<T,int>p=P.front();P.pop();
				if(d[p.second]<p.first)continue;
				for(int i=0;i<G[p.second].size();i++)
				{
					edge&e=G[p.second][i];
					if(e.cap>0&&d[e.to]>d[p.second]+e.cost+h[p.second]-h[e.to])
					{
						d[e.to]=d[p.second]+e.cost+h[p.second]-h[e.to];
						pv[e.to]=p.second;
						pe[e.to]=i;
						P.push(make_pair(d[e.to],e.to));
					}
				}
			}
			if(d[t]==numeric_limits<T>::max())return 1;
			for(int u=0;u<G.size();u++)h[u]+=d[u];
			int d=f;
			for(int u=t;u!=s;u=pv[u])d=min(d,G[pv[u]][pe[u]].cap);
			f-=d;
			ret+=d*h[t];
			for(int u=t;u!=s;u=pv[u])
			{
				G[pv[u]][pe[u]].cap-=d;
				G[u][G[pv[u]][pe[u]].rev].cap+=d;
			}
		}
		return ret;
	}
};
int N;
string s;
int V[2020];
main()
{
	cin>>N>>s;
	for(int i=0;i<N;i++)cin>>V[i];
	vector<pair<pair<int,int>,pair<int,long> > >E;
	int pre[4]={-1,-1,-1,-1};
	int st=N,go=N+1;
	for(int i=N;i--;)
	{
		if(s[i]=='y')
		{
			E.push_back(make_pair(make_pair(st,i),make_pair(1,0)));
			if(pre[1]!=-1)
			{
				E.push_back(make_pair(make_pair(i,pre[1]),make_pair(1,-V[i])));
			}
			pre[0]=i;
		}
		else if(s[i]=='u')
		{
			if(pre[1]!=-1)
			{
				E.push_back(make_pair(make_pair(i,pre[1]),make_pair(N,0)));
			}
			if(pre[2]!=-1)
			{
				E.push_back(make_pair(make_pair(i,pre[2]),make_pair(1,-V[i])));
			}
			pre[1]=i;
		}
		else if(s[i]=='k')
		{
			if(pre[2]!=-1)
			{
				E.push_back(make_pair(make_pair(i,pre[2]),make_pair(N,0)));
			}
			if(pre[3]!=-1)
			{
				E.push_back(make_pair(make_pair(i,pre[3]),make_pair(1,-V[i])));
			}
			pre[2]=i;
		}
		else
		{
			if(pre[3]!=-1)
			{
				E.push_back(make_pair(make_pair(i,pre[3]),make_pair(N,0)));
			}
			E.push_back(make_pair(make_pair(i,go),make_pair(1,-V[i])));
			pre[3]=i;
		}
	}
	MCF<long>P(N+2);
	for(pair<pair<int,int>,pair<int,long> >e:E)P.add_edge(e.first.first,e.first.second,e.second.first,e.second.second);
	long ans=0;
	for(int L=1;;L++)
	{
		long T=P.min_cost_flow(st,go,1);
		if(T>=0)break;
		ans-=T;
	}
	cout<<ans<<endl;
}