That's easy. First guy puts 2 condoms on so inside of the internal one and outside of the external one get "dirty"

Second guy takes out internal one (don't forget, the outside of the internal one is still clean) and puts on the external condom - the women can't get infected since it was inside her already...

Now, third guy takes the internal condom inside-out so its clean surfact touches his body and on the top of it puts the same external that had been inside the woman two times already so again she can't get infected from herself.

I guess this is the only solution, cheers.

BTW, I got my MBA from that school :-)