cepheid

so the difference becomes...

10^4 (a-e) + 10^3 (b-d) + 10^2 (c-c) + 10 (d-b) + (e-a)

= (10^4 - 1)(a-e) + (10^3 - 10)(b-d)

= 9999(a-e) + 990(b-d)

I guess that means the answer is divisible by 9. Did I do this right?