#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <sstream>
#include <algorithm>
#include <stack>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <deque>
#include <functional>
#include <math.h>
#include <complex>
using namespace std;

#include <atcoder/all>
using namespace atcoder;

#define REP(i,n) for(int i = 0; i < (int)n; i++)
#define RREP(i,n) for(int i = (int)n-1; i >= 0; i--)
#define LREP(i,n) for(LL i = 0; i < (LL)n; i++)

#define Vi vector<int>
#define Vl vector<long long>
#define LP pair<long long ,long long>
#define P pair<int, int>
#define T3 tuple<LL, LL, LL>
#define T4 tuple<LL, LL, LL, LL>
#define INF 1000000007
#define SIZE	400010
#define MOD 998244353
typedef long long LL;

LL N;
string S;
LL V[SIZE];

int main() {
	cin >> N >> S;
	REP(i, N) cin >> V[i];

	LL X = INF;
	mcf_graph<LL, LL> graph(N + 2);
	string T = "yuki";
	REP(k, 4) {
		REP(i, N) {
			if (S[i] == T[k]) {
				REP(j, N) {
					if (j <= i) continue;
					if (S[j] == T[k]) {
						graph.add_edge(i, j, INF, 0);
						break;
					}
				}
			}
		}
	}
	REP(i, N) {
		if (S[i] == 'y') {
			graph.add_edge(N, i, INF, 0);
			break;
		}
	}

	REP(k, 3) {
		REP(i, N) {
			if (S[i] == T[k]) {
				REP(j, N) {
					if (j <= i) continue;
					if (S[j] == T[k + 1]) {
						graph.add_edge(i, j, 1, X - V[i]);
						break;
					}
				}
			}
		}
	}

	REP(i, N) {
		if (S[i] == 'i') {
			graph.add_edge(i, N + 1, 1, X - V[i]);
		}
	}

	vector<LP> res = graph.slope(N, N + 1);
	LL ans = 0;
	for (auto p : res) {
		ans = max(ans, -(p.second - 4 * X * p.first));
	}
	cout << ans << endl;
}