import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
sys.setrecursionlimit(10**7)
yes = lambda :print("yes");Yes = lambda :print("Yes")
no = lambda :print("no");No = lambda :print("No")
#######################################################################

a = ni()
b = list(map(int,list(input())))[::-1]
Z = len(b)
ans = 0

p = 10**9+7
for i in range(Z-1):
    ans+=i*(pow(a,i+1,p)-pow(a,i,p))%p
    ans%=p
#print(ans)
ans+=((Z-1)*(b[-1]-1)%p*pow(a,Z-1,p))%p
ans%=p
t = 1
for i in range(Z-1):
    t+=b[i]*pow(a,i,p)
    t%=p
ans+=t*(Z-1)%p
ans%=p
print(ans)