A = int(input())
B = input()
MOD = 10 ** 9 + 7

ans = 0

tmp = (A - 1)
for i in range(len(B) - 1):
    ans += i * tmp
    ans %= MOD
    tmp *= A
    tmp %= MOD

tmp = 0
for s in B:
    n = int(s)
    tmp *= A
    tmp += n
    tmp %= MOD
tmp += 1 - pow(A, len(B) - 1, MOD)
ans += tmp * (len(B) - 1)
ans %= MOD
print(ans)