Let's say I have 3 people who each has a random number:
A: 1920970862902
B: 1920970862087
C: 1920970861233
How do I create a single number $X$ from $N$ (in this case, 3) numbers, where if I give $X$ to $A$, $B$ or $C$, they will be able to use $X$ to determine if their own number is inside? Is this even possible?
Extra Info: I'm using this for a programming function, so I would prefer simple formulas.