# https://yukicoder.me/problems/no/1580

MOD = 10 ** 9 + 7

def main():
    A = int(input())
    B = input()

    b_sum = 0
    for b in B:
        b_sum *= A
        b_sum %= MOD
        b_sum += int(b)
        b_sum %= MOD
    
    answer = 0
    a_prd = A
    for _ in range(1, len(B)):
        answer += (b_sum - a_prd + 1) % MOD
        answer %= MOD

        a_prd *= A
        a_prd %= MOD
    
    print(answer)


    





if __name__ == "__main__":
    main()