n = int(input())
a = list(map(int, input().split()))
s = input().strip()
MOD = 10**9 + 7

from collections import defaultdict

last = defaultdict(int)
dp = 1  # includes empty subsequence initially

for i in range(n):
    c = s[i]
    m = a[i]
    prev_last = last[c]
    # Compute new_dp = (m+1)*dp - m*prev_last mod MOD
    term1 = (m + 1) * dp
    term2 = m * prev_last
    new_dp = (term1 - term2) % MOD
    # Compute new_last = m*dp - (m-1)*prev_last mod MOD
    term3 = m * dp
    term4 = (m - 1) * prev_last
    new_last = (term3 - term4) % MOD
    # Update dp and last[c]
    dp = new_dp
    last[c] = new_last

# Subtract 1 for the empty subsequence
answer = (dp - 1) % MOD
print(answer)