A = int(input())
B = int(input())
B= int(str(B),A)
x = 1
j = A
ans = 0
mod = 10 ** 9 + 7

def check(x):
    return pow(A,x) <= B

lb = 0
ub = 10 ** 5 + 10

while ub - lb > 1:
    mid = (ub + lb) // 2
    if check(mid):
        lb = mid
    else:
        ub = mid

for i in range(lb+1):
    ans = (ans + (A-1) * x * i) % mod
    x = (x * A) % mod
ans = (ans + (B - x + 1) * i) % mod

print(ans)