def main():
    A = int(input()); MOD = pow(10,9) + 7
    B = list(str(input()))
    B = [int(b) for b in B]
    B.reverse()
    N = len(B)
    ans = 0
    powa = 1
    cum = 0
    for i in range(N):
        if i != N-1:
            temp = i*powa*(A-1)%MOD
            cum += powa*B[i]%MOD
            cum %= MOD
        else:
            cum += powa*B[i]%MOD
            temp = i*(cum - powa + 1)%MOD
        #print(i,cum,temp)
        ans += temp
        ans %= MOD
        powa = powa*A%MOD
    print(ans)

if __name__ == '__main__':
    main()