#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
//#include<bits/extc++.h>
//__gnu_pbds
#define pt pair<pair<int,int>,pair<int,int> >
#define xl first.first
#define xr first.second
#define yl second.first
#define yr second.second
const int N = 205;
ll dp[N][N];
string s;
int a,b,c;
const int MOD = 1e9+7;
int hsh[N];
int ppow[N];
int get(int l,int r){
ll ans = hsh[r];
ans = (ans-(1LL*hsh[l-1]*ppow[r-l+1])%MOD)%MOD;
if(ans<0) ans+=MOD;
return ans;
}
int main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
int n;cin>>n;
cin>>s;
cin>>a>>b>>c;
ppow[0]=1;
for(int i=1;i<=n;i++){
hsh[i] = (1LL*hsh[i-1]*31)%MOD;
hsh[i]+=(s[i-1]-'a');
hsh[i]%=MOD;
ppow[i] = (31LL*ppow[i-1])%MOD;
}
for(int i=0;i<=n+1;i++){
for(int j=i;j<=n+1;j++) dp[i][j]=1LL*(j-i+1)*a+b;
}
for(int l=0;l<n;l++){
for(int i=1;i+l<=n;i++){
for(int l2=0;l2<l;l2++){
for(int j=1;j+l2<=n;j++){
ll re = 0;
for(int h=i;h<=i+l;h++){
if(h+l2<=i+l && get(h,h+l2)==get(j,j+l2)){
h= h+l2;
re+=c;
}else{
re+=a;
}
}
// if(dp[i][i+l]>re+dp[j][j+l2]+c){
// cout<<i<<" "<<i+l<<"<-"<<j<<" "<<j+l2<<"\n";
// }
dp[i][i+l] = min(dp[i][i+l],re+dp[j][j+l2]+b);
}
}
// cout<<dp[i][i+l]<<" ";
}
//cout<<"\n";
}
cout<<dp[1][n]-b<<"\n";
return 0;
}
