def modPow(a,n,mod):#繰り返し二乗法 a**n % mod
    if n==0:
        return 1
    if n==1:
        return a%mod
    if n & 1:
        return (a*modPow(a,n-1,mod)) % mod
    t = modPow(a,n>>1,mod)
    return (t*t)%mod

A = int(input())
B = input()
if len(B) == 1:
    print(0)
    exit()
mod = 10**9+7
lB = len(B)
ans = 0
for i in range(1,lB):
    ans += (i-1)*(modPow(A,i,mod)-modPow(A,i-1,mod))
    ans %= mod
ans += (modPow(A,lB-1,mod))*(int(B[0])-1)*(lB-1)
ans %= mod
ad = 1
cc = 1
for i in range(1,lB):
    ad += cc*int(B[-i])
    cc *= A
    cc %= mod
    ad %= mod
ad *= lB-1
print((ans+ad)%mod)