@Kejero
I did not understand well this :
A single monk can see all the other monks, and see if another monk has a dot on his head or no, but he cannot see himself,
I thought that "a single monk" meaned "only one monk", so i have made a mistake.
Then i thought that everyone, even a monk, will be feared to sacrifice himself.
This idea of topic is good, the forum is a little bit sleepy since a few days.
Barta