## https://yukicoder.me/problems/no/1845

MOD = 10 ** 9 + 7

def main():
    N = int(input())
    A = list(map(int, input().split()))
    S = input()

    dp = [0] * (N + 1)
    dp[0] = 1
    last_alphabet_index = [0] * 26

    first_dp = [0] * (N + 1)
    first_dp[0] = 1
    total_dp = [0] * (N + 1)
    total_dp[0] = 1
    cum_total_dp = [0] * (N + 1)
    cum_total_dp[0] = 1
    for i in range(N):
        a = S[i]

        # first_xを求める
        last = last_alphabet_index[ord(a) - ord("a")]
        x = (cum_total_dp[i] - cum_total_dp[last]) % MOD
        x += first_dp[last]
        x %= MOD

        first_dp[i + 1] = x
        total_dp[i + 1] = (x * A[i]) % MOD
        cum_total_dp[i + 1] = (cum_total_dp[i] + total_dp[i + 1]) % MOD

        last_alphabet_index[ord(a) - ord("a")] = i + 1

    answer = (cum_total_dp[N]  - cum_total_dp[0]) % MOD
    print(answer)



        







    


        

    



if __name__ == "__main__":
    main()