You are the owner of a marble warehouse where you store marbles in buckets. You can fit any number of marbles in one bucket. Your job is to store X marbles in a minimal number of buckets. But, when a customer comes and asks for Y number of marbles, you must be able to hand over some buckets and give them the exact number, without adding/removing marbles from the buckets. Essentially, minimize the number of buckets while maintaining countability. I was asked this question in a job interview, and would like to hear your answers.