import heapq
class MinCostFlow:
    def __init__(self, n):
        self.n=n
        self.g=[[] for _ in range(n)]
        self.h=[0]*n
    def add_edge(self, frm, to, cap, cost):
        g=self.g
        g[frm].append((to, cap, cost, len(g[to])))
        g[to].append((frm, 0, -cost, len(g[frm])-1))
    def mincostflow(self, s, t, f):
        res=0
        n=self.n
        g=self.g
        h=self.h
        INF=10**18
        h=[0]*n
        prevv=[0]*n
        preve=[0]*n
        while f>0:
            que=[]
            dist=[INF]*n
            dist[s]=0
            heapq.heappush(que, s)
            while len(que)>0:
                p=heapq.heappop(que)
                v=(p&((1<<20)-1))
                if dist[v]<(p>>20):
                    continue
                for i, e in enumerate(g[v]):
                    to, cost=e[0], e[2]
                    if e[1]>0 and dist[to]>dist[v]+cost+h[v]-h[to]:
                        dist[to]=dist[v]+cost+h[v]-h[to]
                        prevv[to]=v
                        preve[to]=i
                        heapq.heappush(que, (dist[to]<<20)^to)
            for i, d in enumerate(dist):
                h[i]+=d
            if dist[t]==INF:
                return -1
            d=f
            v=t
            while v!=s:
                d=min(d, g[prevv[v]][preve[v]][1])
                v=prevv[v]
            f-=d
            res+=d*h[t]
            v=t
            def add(e, d):
                return (e[0], e[1]+d, e[2], e[3])
            while v!=s:
                g[prevv[v]][preve[v]]=add(g[prevv[v]][preve[v]], -d)
                rev=g[prevv[v]][preve[v]][3]
                g[v][rev]=add(g[v][rev], d)
                v=prevv[v]
        return res
n=int(input())
s=input()
v=list(map(int, input().split()))
start, end, S, T=n+1, n, n+2, n+3
mcf=MinCostFlow(n+4)
mcf.add_edge(S, start, n//4, 0)
mcf.add_edge(end, T, n//4, 0)
ans=0
f=0
s0="yuki"
idx=[n+1]*5
idx[4]=n
for i in range(n-1, -1, -1):
    k=s0.find(s[i])
    if idx[k]<=n:
        mcf.add_edge(i, idx[k], n//4, 0)
    if idx[k+1]<=n:
        mcf.add_edge(S, idx[k+1], 1, 0)
        mcf.add_edge(idx[k+1], i, 1, v[i])
        mcf.add_edge(i, T, 1, 0)
        ans+=v[i]
        f+=1
    idx[k]=i
if idx[0]<=n:
    mcf.add_edge(start, idx[0], n//4, 0)
mcf.add_edge(start, end, n//4, 0)
ans-=mcf.mincostflow(S, T, n//4+f)
print(ans)