MOD = 10 ** 9 + 7

n = int(input())
A = list(map(int, input().split()))
S = input()
dp = [0] * 26

for a, s in zip(A, S):
    p = ord(s) - 97
    dp[p] += a * (sum(dp) - dp[p] + 1) % MOD
    dp[p] %= MOD
print(sum(dp) % MOD)