When prompted, answer how many people you wish to attend a party. Scratch Cat will then tell you whether anyone shares any birthdays, and if so, who shares birthdays and on what date. The lists correspond, so if the person in slot 4 of the 'People' list is called 'Benjamin Moore' the date in slot 4 of the 'Birthdays' list shows Benjamin Moore's birthday.
[NOTE: THERE MUST BE BETWEEN 2-365 PARTY ATTENDEES OTHERWISE IT WILL NOT WORK] The reason this is considered a paradox is because, with as little as 23 partygoers, the chance that two or more people would share a birthday would be over 50%, despite the fact that it sounds too small of a quantity.