Is the woman the only concern? Then one condom is just fine. The outside is always for the woman, the 3 man who cares. Seeing the financial crisis I like this answer. haha.
Or, I don't want to give specifics on public forum (you guys know anyways) ... the woman could use alternative way to have sex with at least one of the guys.
Or, assuming the woman is safe the guys may not. Man1 use C1, Man2 use C2, Man3 take C1, reverse it, put it on, then put on C2 on top of that ..
Do I get a wall street job?