Maintaining while on vacation

[Actual God]

Hi,

I started lifting about five months ago at 5'11 / 150 lbs and gained about nine pounds and a decent amont of strength using basically rippetoe method plus pull-ups and dips.

A few days ago I left for Europe. I'll be gone for about 4 months. I've been doing pushups and weightless squats whenever the spirit moves me, but I feel like I'm going to lose all my hard-earned gains.

I'll start looking for random places to do pull-ups - I guess that'll help. Anything else I can do? If there's an optimal way to do pushups and weightless squats, I'd love to hear it, although I assume "as many as possible" is the best strategy.

Thanks,
AG