MOD = 10 ** 9 + 7
A = int(input())
B = list(map(int, input()[::-1]))
Ans = 0
for i in range(len(B) - 1):
    Ans += pow(A, i, MOD) * (A - 1) * i
    Ans %= MOD
B[-1] -= 1
Num = 1
for i in range(len(B)):
    Num += B[i] * pow(A, i, MOD) % MOD
    Num %= MOD
Ans += Num * (len(B) - 1) % MOD
Ans %= MOD
print(Ans)