代码：

#include<bits/stdc++.h>
using namespace std;
const int inf = 1e9;
const int mm = 111111;
const int maxn = 2999;
int node,src,dest,edge;
int ver[mm],flow[mm],cst[mm],nxt[mm];
int head[maxn],work[maxn],dis[maxn],q[maxn];
int tot_cost;
void prepare(int _node,int _src,int _dest)
{node=_node,src=_src,dest=_dest;for(int i=0; i<node; ++i)head[i]=-1;edge=0;tot_cost = 0;
}
void add_edge(int u,int v,int c,int cost)
{ver[edge]=v,flow[edge]=c,nxt[edge]=head[u],cst[edge]=cost,head[u]=edge++;ver[edge]=u,flow[edge]=0,nxt[edge]=head[v],cst[edge]=-cost,head[v]=edge++;
}
int ins[maxn];
int pre[maxn];
bool Dinic_spfa()
{memset(ins,0,sizeof(ins));memset(dis,-1,sizeof(dis));memset(pre,-1,sizeof(pre));queue<int> Q;//int i,u,v,l,r=0;Q.push(src);dis[src] = 0,ins[src] = 1;pre[src] = -1;while(!Q.empty()){int u = Q.front();Q.pop();ins[u] = 0;for(int e = head[u];e != -1;e = nxt[e]){int v = ver[e];if(!flow[e]) continue;if(dis[v] < 0 || dis[v] > dis[u] + cst[e]){dis[v] = dis[u] + cst[e];pre[v] = e;if(!ins[v]) ins[v] = 1,Q.push(v);}}    	}return dis[dest] != -1;
}
int Dinic_flow()
{int i,ret=0,delta=inf;while(Dinic_spfa()){for(int i=pre[dest];i != -1;i = pre[ver[i^1]])delta = min(delta,flow[i]);for(int i=pre[dest];i != -1;i = pre[ver[i^1]])flow[i] -= delta,flow[i^1] += delta;ret+=delta;tot_cost += dis[dest]*delta;}return ret;
}
int abc[27];
int ag[111];
int val[111];
int n;
int main(){int sum = 0;scanf("%d",&n);prepare(1+26+n/2*26+n+1,0,1+26+n/2*26+n);for(int i = 1;i <= n;++i){char c;scanf(" %c",&c);abc[c-'a'+1]++;ag[i] = c-'a'+1;}for(int i = 1;i <= n;++i){scanf("%d",&val[i]);sum += val[i];}for(int i = 1;i <= 26;++i) add_edge(0,i,abc[i],0);for(int i = 1;i <= 26;++i){for(int j = 1;j <= n/2;j++){int _a = 26+(i-1)*n/2+j;add_edge(i,_a,1,0);int f1 = j,f2 = n-j+1;if(ag[f1] == i) add_edge(_a,f1+26+26*n/2,1,0);else add_edge(_a,f1+26+26*n/2,1,val[f1]);if(ag[f2] == i) add_edge(_a,f2+26+26*n/2,1,0);else add_edge(_a,f2+26+26*n/2,1,val[f2]);}}for(int i = 1;i <= n;++i) add_edge(26+26*n/2+i,1+26+n/2*26+n,1,0);int f = Dinic_flow();//cout<<f<<endl;cout<<sum - tot_cost<<endl;return 0;
}