import sys
input = sys.stdin.readline

N = int(input())
A = list(map(int, input().split()))
S = input()[:-1]
dp = [0]*(N+1)
dp[0] = 1
prev = [-1]*26
acc = [0]
MOD = 10**9+7

for i in range(N):
    j = prev[ord(S[i])-ord('a')]
    dp[i+1] = (acc[-1]-acc[j+1]+dp[j+1])%MOD
    acc.append((acc[-1]+dp[i+1]*A[i])%MOD)
    prev[ord(S[i])-ord('a')] = i

print(acc[-1])