#pragma GCC optimize("Ofast","O3","unroll-loops")
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define x first
#define y second
#define pii pair<int,int>
#define all(x) x.begin(),x.end()
const int INF=1e9;
int k=31,mod=1e9+7;
struct Hash{
vector<int> pw,h;
Hash(string s){
int n=s.size();
s=' '+s;
pw.resize(n+2);
h.resize(n+2);
pw[0]=1;
for(int i=1;i<=n;i++){
pw[i]=pw[i-1]*k%mod;
h[i]=h[i-1]*k+s[i]-'a'+1;
h[i]%=mod;
}
}
int get(int a,int b){
a++;b++;
int len=b-a;
return ((h[b-1]-h[a-1]*pw[len])%mod+mod)%mod;
}
};
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
int n;cin>>n;
string s;cin>>s;
Hash h(s);
int a,b,c;cin>>a>>b>>c;
bool flag=0;
for(int i=0;i<n;i++){
if(s[i]!='a'){
flag=1;
}
}
if(flag==0){
vector<vector<int>> dp(n+1,vector<int>(n+1,INF));
dp[0][0]=0;
for(int i=0;i<=n;i++){
for(int j=i;j<=n;j++){
dp[i][j]=min(dp[i][j],dp[i][j-i]+c);
dp[i][j]=min(dp[i][j],dp[i][j-1]+a);
dp[j][0]=min(dp[j][0],dp[i][j]+b);
}
}
int ans=INF;
for(int i=0;i<=n;i++){
ans=min(ans,dp[i][n]);
}
cout<<ans<<endl;
return 0;
}
//cout<<h.get(2,5)<<' '<<h.get(5,8)<<endl;
vector<vector<int>> dp(n+2,vector<int>(n+2));
for(int len=1;len<=n;len++){
for(int i=0;i+len<=n;i++){
int r=i+len;
//cout<<i<<' '<<r<<endl;
dp[i][r]=len*a+b;
for(int i1=i;i1<r;i1++){
for(int j1=i1+1;j1<=r;j1++){
int len1=j1-i1;
int cnt=0;
for(int p=i;p+len1<=r;p++){
if(h.get(i1,j1)==h.get(p,p+len1)){
cnt++;
p=p+len1-1;
}
}
dp[i][r]=min(dp[i][r],dp[i1][j1]+cnt*c+(len-len1*cnt)*a+b);
}
}
}
}
cout<<dp[0][n]-b<<endl;
return 0;
}
