Zilch
This...is...Caketown!
I don't want to make this into a pissing match, but if the most you run is four miles, you should be ok, I think. Marine OCS has the candidates run 3 miles to start out, and that's the shortest distance you run the entire 10 weeks. I don't bring this up to compare the two, really, I just wanted to point out that Marine candidates do it all the time, and they graduate just fine. Well...usually. The big deal is to stretch, stretch, stretch, and, most importantly, arrive in shape. By that, I mean don't overtrain so you're broke when you get there, and don't undertrain so you get injured when you have to push hard all the time to keep up. You'll be alright.