12 or 13?

I received this e-mail a couple of days ago. This seems extraordinarily impossible. I'm stunned. 

12 or 13?     

This is the cleverest email.

Please wait until the group changes positions.

Is it twelve or thirteen??
<> 

This will drive you crazy!

Where does the extra man come from?

Don't ask me; I haven't figured it out yet!!

Neat trick.

good one.. but i can see a difference on top piece.. on one side it is 3 and on another only 2... but appreciate the idea..