MOD = 1000000007

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

dp = [ 0 ] * N
dpsum = [ 0 ] * 26
dpallsum = 0
for i in range(0, N):
	ch = ord(S[i]) - ord('a')
	dp[i] = ((1 + (dpallsum - dpsum[ch])) * A[i]) % MOD
	dpsum[ch] += dp[i]
	dpallsum += dp[i]

print(sum(dp) % MOD)