N=int(input())
A=list(map(int,input().split()))
S=input()
M=10**9+7
p=[0]*26
dp=[0]*N
sum=[0]*(N+1)
ans=0
for i in range(N):
	c=ord(S[i])-ord('a')
	tmp=p[c]
	p[c]=i+1
	dp[i]=sum[i]
	if tmp==0:
		dp[i]+=1
	else:
		dp[i]-=sum[tmp]
		dp[i]+=dp[tmp-1]
	sum[i+1]=(A[i]*dp[i])%M
	sum[i+1]+=sum[i]
	sum[i+1]%=M
print(sum[N])