MOD = 10**9+7
A = int(input())
B = list(map(int,list(input())))[::-1]
K = len(B)
ans = 0
for k in range(K-1):
    ans = (ans+k*(A-1)*pow(A,k,MOD))%MOD
ans = (ans+(K-1)*(B[K-1]-1)*pow(A,K-1,MOD))%MOD
cnt = 0
for k in range(K-1):
    cnt = (cnt+B[k]*pow(A,k,MOD))%MOD
cnt += 1
ans = (ans+(K-1)*cnt)%MOD
print(ans)