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The two people that jumped off the cliff are equivalent to 2.5 people.

Then... If XX = 99999

Then X is 99 + 9/2 😆

I get to this x*ln(x)=ln(99999) which needs some approximation methods (numerical) nad that is something I do not have a time to do ;-).

It looks I have got some time :-).
It is 6,2709 (for 4 numbers after the decimal point...)