I agree with O&G. Finding your maxes after 3 months off would probably cause extreme soreness and a bit of conditioning to the weights (so the 15's later wouldn't be as much effective). You are pretty deconditioned now and I guess that even previously "easy" weights will get the job done (cause microtrauma, that is). Try to estimate your maxes for each rep range, taking into account your previous lifts and allow for a reduction in the weight due to your 3 month absence. Start right away and repeat weights if necessary. By the time you get to the 10's you should be on your way.