Gabriel V. answered 08/09/19
Master Mathematics and Science Teacher, ACT/SAT Test Prep Tutor
This looks similar to the birthday problem that uses the pigeonhole principle. If you don't know about it it is interesting and may help you with your problem. I would think that the number in your problem is going to be real close to 100%!
In probability theory, the birthday problem or birthday paradox concerns the probability that, in a set of n randomly chosen people, some pair of them will have the same birthday. By the pigeonhole principle, the probability reaches 100% when the number of people reaches 367 (since there are only 366 possible birthdays, including February 29). However, 99.9% probability is reached with just 70 people, and 50% probability with 23 people. These conclusions are based on the assumption that each day of the year (excluding February 29) is equally probable for a birthday.