There are 100 prisoners, each prisoner is given a number between 1 and 100 without knowing which number, the number can repeat and not all of the numbers must be given.
Each prisoner in his turn can guess his number, if he succeed, all of the prisoners are freed (they cant hear the other guesses).
Each prisoner is also given a list of the other prisoners numbers.
The prisoners have a chance to plot their strategy before the list is given.
What is the optimal plan?