schoolwork 2nd

// #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;
	
}