Cover letter while applying to 2 offices in separate countries

Hello!

So I am applying to Bain's Singapore and Australian offices, i.e. Singapore and Sydney. The website allows a candidate to only submit one application. So how do I explain my choice of office locations in a single cover letter? Do I not talk about specific locations but just my motivation for international exposure? Or do I create a separate account and apply separately for different countries? Or mention motivation for both locations in the same letter?

I'm angry at myself for being stuck at such a stupid problem. Damn.