Not quite sure what these guys were doing — but they did it in style:
The photo (click for bigger) was shot by Jean Cocteau in 1916. According to the caption it features Picasso, Kisling, Paquerette, and M Vassilieff, but I can count only three men. The one on the right is probably Picasso.

Interesting photo.
The one on the right is definitely Picasso.
Moise Kisling was a famous Montparnasse painter and Paquerette a model.
Now, the person in the back is not M. ( Mister ) Vassilieff, but Marie Vasillieff, Russian artist, mostly famous for the “cantine” or home-restaurant, she ran in Montparnasse during WWI, and where so many artists used to meet and eat. This is where Modigliani was threatened with a pistol by the new lover of a former mistress, and many other stories…
The place is now the Musée du Montparnasse.
Thanks for the clarification, Alain!
Vassilieff is Marie Vassilieff, SHE’s in the middle.