MOD = 10**9 + 7

def main():
    import sys
    input = sys.stdin.read().split()
    idx = 0
    N = int(input[idx])
    idx += 1
    A = list(map(int, input[idx:idx+N]))
    idx += N
    S = input[idx]
    
    total = 1
    from collections import defaultdict
    last = defaultdict(int)
    
    for i in range(N):
        c = S[i]
        m = A[i]
        prev_total = total
        prev_last = last[c]
        
        new_total = ( ( (m + 1) * prev_total - m * prev_last ) % MOD + MOD ) % MOD
        new_last = ( ( m * prev_total - (m - 1) * prev_last ) % MOD + MOD ) % MOD
        
        total = new_total
        last[c] = new_last
    
    answer = (total - 1 + MOD) % MOD
    print(answer)

if __name__ == "__main__":
    main()