n = int(input())
A = list(map(int,input().split()))
S = input()
mod = 10**9+7
next = [[n]*26 for i in range(n+1)]
for i in range(n)[::-1]:
    s = ord(S[i])-ord("a")
    for j in range(26):
        if j == s:
            next[i][j] = i
        else:
            next[i][j] = next[i+1][j]


dp = [0]*(n+2)
for i in range(26):
    if next[0][i] != n:
        dp[next[0][i]] += 1

ans = 0
for i,(a,s) in enumerate(zip(A,S)):
    s = ord(s)-ord("a")
    ans += dp[i]*a
    ans %= mod
    for j in range(26):
        if s == j:
            dp[next[i+1][j]] += dp[i]
        else:
            dp[next[i+1][j]] += dp[i]*a%mod
        dp[next[i+1][j]] %= mod

print(ans)