using factorial in probability question

[resolved]

software version 10024
hardware version C

I will update later -- calculator just purchased a few days ago

Problem: what is the probability of 2 people having the same birthday amongst 30 people???

Solution: 1 - 365! / ((365-30)!*365^30) = 0.706316

my answer on the HP Prime is +inf --- not good
in HOME the highest factorial I can get is 253! before it max out
in CAS the highest factorial I can get is 170! before I get +inft

in HOME 365! / 253! i get 0
365! / 252! i get 489.03

In CAS 365! / 252! i get a huge number several 100 digits long

how can I solve this problem on the HP Prime????