using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;


using P = pair<int, int>;

class Program
{
  Scanner cin;
  Printer cout;

  void myon()
  {
    cin = new Scanner();
    cout = new Printer();


    int N = cin.nextInt();
    String s = cin.next();
    long[] A = cin.nextArrayLong(N);

    var MCF = new MinCostFlow(N + 1);

    int[] nxt = new int[5];
    nxt[0] = N + 1;
    nxt[1] = N + 1;
    nxt[2] = N + 1;
    nxt[3] = N + 1;
    nxt[4] = N;

    const String t = "yuki";
    const long inf = 1000000000;
    for(int i = N - 1; i >= 0; i--)
    {
      int k = t.IndexOf(s[i]);
      if (nxt[k] <= N)
      {
        MCF.addEdge(i, nxt[k], N / 4, 0);
      }
      if (nxt[k + 1] <= N)
      {
        MCF.addEdge(i, nxt[k + 1], 1, inf - A[i]);
      }
      nxt[k] = i;
    }
    if(nxt[0] == N + 1)
    {
      cout.println("0");
      return;
    }
    MCF.addEdge(nxt[0], N, N / 4, inf * 4);
    cout.println(inf * 4 * (N / 4) - MCF.run(nxt[0], N, N / 4));
  }


  static void Main(string[] args)
  {
    new Program().myon();
  }
}


class Printer
{
  public Printer()
  {
    var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
    Console.SetOut(sw);
  }

  ~Printer()
  {
    flush();
  }

  public void println(string a)
  {
    Console.WriteLine(a);
  }

  public void println<T>(IEnumerable<T> a)
  {
    println(string.Join(" ", a));
  }
  public void println(params object[] a)
  {
    println(string.Join(" ", a));
  }

  public void print<T>(string a)
  {
    Console.Write(a);
  }

  public void print<T>(IEnumerable<T> a)
  {
    print(string.Join(" ", a));
  }

  public void print(params object[] a)
  {
    print(string.Join(" ", a));
  }

  public void printArray<T>(params T[] a)
  {
    foreach (var x in a) Console.WriteLine(x);
  }
  public void flush() => Console.Out.Flush();
}

class Scanner
{
  readonly CultureInfo ci = CultureInfo.InvariantCulture;
  string[] s;
  int i;
  readonly char[] cs = new char[] { ' ' };

  public Scanner()
  {
    s = new string[0];
    i = 0;
  }

  public string next()
  {
    if (i < s.Length) return s[i++];
    string st = Console.ReadLine();
    while (st == "") st = Console.ReadLine();
    s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
    if (s.Length == 0) return next();
    i = 0;
    return s[i++];
  }

  public string nextLine()
  {
    return Console.ReadLine();
  }

  public int nextInt()
  {
    return int.Parse(next());
  }

  public long nextLong()
  {
    return long.Parse(next());
  }

  public double nextDouble()
  {
    return double.Parse(next(), ci);
  }
  public int[] nextArrayInt(int N, int add = 0)
  {
    int[] ret = new int[N];
    for (int i = 0; i < N; i++)
    {
      ret[i] = nextInt() + add;
    }
    return ret;
  }

  public long[] nextArrayLong(int N, long add = 0)
  {
    long[] ret = new long[N];
    for (int i = 0; i < N; i++)
    {
      ret[i] = nextLong() + add;
    }
    return ret;
  }

  public double[] nextArrayDouble(int N, double add = 0)
  {
    double[] ret = new double[N];
    for (int i = 0; i < N; i++)
    {
      ret[i] = nextDouble() + add;
    }
    return ret;
  }
}



class pair<T, U> : IComparable<pair<T, U>>
{
  public T v1;
  public U v2;
  public pair() : this(default(T), default(U)) { }
  public pair(T v1, U v2) { this.v1 = v1; this.v2 = v2; }
  public int CompareTo(pair<T, U> a)
  {
    int c = Comparer<T>.Default.Compare(v1, a.v1);
    return c != 0 ? c : Comparer<U>.Default.Compare(v2, a.v2);
  }
  public override string ToString() => v1 + " " + v2;
  public void Deconstruct(out T a, out U b) { a = v1; b = v2; }
}
static class util
{
  public static readonly int M = 1000000007;
  // public static readonly int M = 998244353;
  public static readonly long LM = 1L << 60;
  public static readonly double eps = 1e-11;
  public static void DBG(string a) => Console.Error.WriteLine(a);
  public static void DBG<T>(IEnumerable<T> a) => DBG(string.Join(" ", a));
  public static void DBG(params object[] a) => DBG(string.Join(" ", a));
  public static void Assert(params bool[] conds)
  {
    if (conds.Any(x => !x)) throw new Exception();
  }
  public static pair<T, U> make_pair<T, U>(T v1, U v2) => new pair<T, U>(v1, v2);
  public static int CompareList<T>(IList<T> a, IList<T> b) where T : IComparable<T>
  {
    for (int i = 0; i < a.Count && i < b.Count; i++)
      if (a[i].CompareTo(b[i]) != 0) return a[i].CompareTo(b[i]);
    return a.Count.CompareTo(b.Count);
  }
  public static bool inside(int i, int j, int h, int w) => i >= 0 && i < h && j >= 0 && j < w;
  public static readonly int[] dd = { 0, 1, 0, -1 };
  // static readonly string dstring = "RDLU";
  public static IEnumerable<P> adjacents(int i, int j)
      => Enumerable.Range(0, dd.Length).Select(k => new P(i + dd[k], j + dd[k ^ 1]));
  public static IEnumerable<P> adjacents(int i, int j, int h, int w)
      => adjacents(i, j).Where(p => inside(p.v1, p.v2, h, w));
  public static IEnumerable<P> adjacents(this P p) => adjacents(p.v1, p.v2);
  public static IEnumerable<P> adjacents(this P p, int h, int w) => adjacents(p.v1, p.v2, h, w);
  public static IEnumerable<int> all_subset(this int p)
  {
    for (int i = 0; ; i = i - p & p)
    {
      yield return i;
      if (i == p) break;
    }
  }
  public static Dictionary<T, int> compress<T>(this IEnumerable<T> a)
      => a.Distinct().OrderBy(v => v).Select((v, i) => new { v, i }).ToDictionary(p => p.v, p => p.i);
  public static Dictionary<T, int> compress<T>(params IEnumerable<T>[] a) => compress(a.SelectMany(x => x));
  public static T[] inv<T>(this Dictionary<T, int> dic)
  {
    var res = new T[dic.Count];
    foreach (var item in dic) res[item.Value] = item.Key;
    return res;
  }
  public static void swap<T>(ref T a, ref T b) where T : struct { var t = a; a = b; b = t; }
  public static void swap<T>(this IList<T> a, int i, int j) where T : struct { var t = a[i]; a[i] = a[j]; a[j] = t; }
  public static T[] copy<T>(this IList<T> a)
  {
    var ret = new T[a.Count];
    for (int i = 0; i < a.Count; i++) ret[i] = a[i];
    return ret;
  }
}

class MinCostFlow
{
  class edge
  {
    public int to, cap, rev;
    public long cost;
    public edge(int to, int cap, long cost, int rev)
    {
      this.to = to;
      this.cap = cap;
      this.cost = cost;
      this.rev = rev;
    }
  }
  int n;
  List<edge>[] g;

  public MinCostFlow(int n)
  {
    this.n = n;
    g = new List<edge>[n];
    for (int i = 0; i < n; i++)
      g[i] = new List<edge>();
  }
  public void addEdge(int from, int to, int cap, long cost)
  {
    g[from].Add(new edge(to, cap, cost, g[to].Count));
    g[to].Add(new edge(from, 0, -cost, g[from].Count - 1));
  }
  public long run(int s, int t, int f)
  {
    long res = 0;
    var h = new long[n];
    while (f > 0)
    {
      var q = new PriorityQueue<pair<long, int>>() { rev = true };
      var dist = new long[n];
      var prevv = new int[n];
      var preve = new int[n];
      for (int i = 0; i < n; i++) dist[i] = util.LM;
      dist[s] = 0;
      q.Push(new pair<long, int>(0, s));
      while (q.Count > 0)
      {
        var p = q.Pop();
        int v = p.v2;
        if (dist[v] < p.v1) continue;
        for (int i = 0; i < g[v].Count; ++i)
        {
          var e = g[v][i];
          if (e.cap > 0 && dist[e.to] > dist[v] + e.cost + h[v] - h[e.to])
          {
            dist[e.to] = dist[v] + e.cost + h[v] - h[e.to];
            prevv[e.to] = v;
            preve[e.to] = i;
            q.Push(new pair<long, int>(dist[e.to], e.to));
          }
        }
      }
      if (dist[t] == util.LM) break;
      for (int v = 0; v < n; ++v) h[v] += dist[v];

      int d = f;
      for (int v = t; v != s; v = prevv[v]) d = Math.Min(d, g[prevv[v]][preve[v]].cap);

      f -= d;
      res += d * h[t];
      for (int v = t; v != s; v = prevv[v])
      {
        var e = g[prevv[v]][preve[v]];
        e.cap -= d;
        g[v][e.rev].cap += d;
      }
    }
    return res;
  }
}

// the greatest element pops
class PriorityQueue<T>
{
  List<T> buf;
  public bool rev = false;
  Func<int, int, int> cmp;
  public PriorityQueue()
  {
    buf = new List<T>();
    cmp = (i, j) => Comparer<T>.Default.Compare(buf[i], buf[j]) * (rev ? -1 : 1);
  }
  public PriorityQueue(Func<T, T, int> cmp)
  {
    buf = new List<T>();
    this.cmp = (i, j) => cmp(buf[i], buf[j]);
  }
  void swap(int i, int j) { var t = buf[i]; buf[i] = buf[j]; buf[j] = t; }
  public void Push(T elem)
  {
    int n = buf.Count;
    buf.Add(elem);
    while (n > 0)
    {
      int i = (n - 1) >> 1;
      if (cmp(n, i) <= 0) break;
      swap(i, n);
      n = i;
    }
  }
  public T Pop()
  {
    T ret = buf[0];
    int n = buf.Count - 1;
    buf[0] = buf[n];
    buf.RemoveAt(n);
    for (int i = 0, j; (j = (i << 1) | 1) < n; i = j)
    {
      if (j != n - 1 && cmp(j, j + 1) < 0) ++j;
      if (cmp(i, j) < 0) swap(i, j);
      else break;
    }
    return ret;
  }
  public T Top => buf[0];
  public int Count => buf.Count;
}