import sys
input=sys.stdin.readline
# 最小費用流
from heapq import heappush, heappop
class MinCostFlow:
  INF = 10**18

  def __init__(self, N):
    self.N = N
    self.G = [[] for i in range(N)]

  def add_edge(self, fr, to, cap, cost):
    forward = [to, cap, cost, None]
    backward = forward[3] = [fr, 0, -cost, forward]
    self.G[fr].append(forward)
    self.G[to].append(backward)

  def flow(self, s, t, f):
    N = self.N; G = self.G
    INF = MinCostFlow.INF

    res = 0
    H = [0]*N
    prv_v = [0]*N
    prv_e = [None]*N

    d0 = [INF]*N
    dist = [INF]*N

    while f:
      dist[:] = d0
      dist[s] = 0
      que = [(0, s)]

      while que:
        c, v = heappop(que)
        if dist[v] < c:
          continue
        r0 = dist[v] + H[v]
        for e in G[v]:
          w, cap, cost, _ = e
          if cap > 0 and r0 + cost - H[w] < dist[w]:
            dist[w] = r = r0 + cost - H[w]
            prv_v[w] = v; prv_e[w] = e
            heappush(que, (r, w))
      if dist[t] == INF:
        return res
        return None

      for i in range(N):
        H[i] += dist[i]

      d = f; v = t
      while v != s:
        d = min(d, prv_e[v][1])
        v = prv_v[v]
      f -= d
      res += d * H[t]
      v = t
      while v != s:
        e = prv_e[v]
        e[1] -= d
        e[3][1] += d
        v = prv_v[v]
    return res

def main1(n,s,v):
  mcf=MinCostFlow(n+2)
  inf=10**9
  # n->n+1
  ary=[-1]*5
  ary[4]=n+1
  d={'y':0,'u':1,'k':2,'i':3}
  for i in range(n-1,-1,-1):
    k=d[s[i]]
    if ary[k]!=-1:
      mcf.add_edge(i,ary[k],n//4,0)
    if ary[k+1]!=-1:
      mcf.add_edge(i,ary[k+1],1,-v[i])
    ary[k]=i
  if ary[0]==-1:
    print(0)
    exit()
  mcf.add_edge(n,ary[0],n//4,0)
  return -mcf.flow(n,n+1,n//4)

if __name__=='__main__':
  n=int(input())
  s=list(input())
  v=list(map(int,input().split()))
  ret1=main1(n,s,v)
  print(ret1)