Simple Probabilty Question

[HP]

This has no poker in it so if mods want to move this to SMP I understand

Suppose you have some data on a variable. The only possible values for the variable are 0 and 1

You have no idea where this data comes from

We get 100 data points. We end up with X 1's, and (100-X) 0's. There is a 101th data point, but we haven't been told what it is yet

Call the chance the 101th data point is a 1 'P'

How do we find the probability distribution for P?