These charlatans operate a phony gambling operation with 3 discs; one with a white square underneath. All 4 plus another guy (not in shot) operate the scam. The switch the discs when your not looking. Just let them play by themselves.
Believe me they were not very happy with me taking photos! At the first sign of 'trouble' they scamper in the alleyways. The were operating just down from the Sacré-Cœur Basilica, Paris.