def alp_to_num(cha):
    num = ord(cha) - ord("a")
    return num

N = int(input())
A = list(map(int, input().split()))
mod = 10 ** 9 + 7
S = list(input())
S = list(map(alp_to_num, S))

pre = [0] * 27
pre[26] = 1
psm = 1
for i in range(N):
    dp = [0] * 27
    sm = 0
    dp[S[i]] += (psm - pre[S[i]]) * A[i]
    for c in range(27):
        dp[c] += pre[c]
        sm += dp[c]
        dp[c] %= mod
        sm %= mod
    dp, pre = pre, dp
    sm, psm = psm, sm 
print(sum(pre[:26])% mod)