学業第二

// #2分段
#include<bits/stdc++.h>
using namespace std;

const int maxn = 2005;
int n, w[maxn];
char s[maxn];


int val[maxn][maxn];
void calc_val()
{
    for(int i=1; i<n; ++i) if(s[i] != s[i+1]) val[i][i+1] = min(w[i], w[i+1]);
    for(int len = 4; len <= n; ++ len)
        for(int i=1; i+len-1 <= n; ++i)
            if(s[i] != s[i+len-1])
                val[i][i+len-1] = val[i+1][i+len-2] + min(w[i], w[i+len-1]);
            else
                val[i][i+len-1] = val[i+1][i+len-2];
}

int f[maxn];

int main()
{
    
    scanf("%d", &n);
    scanf("%s", s + 1);
    for(int i=1;i<=n;++i) scanf("%d", &w[i]);
    calc_val();
    
    
    memset(f, 63, sizeof f);
    f[0] = 0;
    for(int i=2; i<=n; i+=2)
        for(int j=0; j<=i-2; j+=2)
            f[i] = min(f[i], f[j] + val[j+1][i]);
    
    cout << f[n];
    
    return 0;
    
}