mod = 10 ** 9 + 7
A = int(input())
B = input()
m = len(B)
DB = 0
for i in range(m):
    DB *= A
    DB += int(B[i])
    DB %= mod

AA = 1
ans = 0
pre = A
i = 0
for i in range(1,m-1):
    now = pre * A
    now %= mod
    ans += (now - pre) * i
    ans %= mod
    pre = now
if m > 1:
    ans += (DB - pre + 1) * (i + 1)
    ans %= mod
print(ans)