The story takes place in a monastory.

On Sundays evenings, the patriarch makes an announcement to all the monks:
A curse has knocked the monastory: the cursed monks have on the forehead a small red mark.

In this convent, there is no slightest mirror,
And the monks have no right to communicate between them in any way,
But prayer in common takes place every day.

Every monk who is certain to be cursed commits suicide in the evening when he discovers it.
From Monday till Saturday, nothing happens. Sunday evening, all cursed monks commited suicide.

How many monks were cursed?