A man came to the farmers market and asked for two carrots. He got two carrots, put them in his ears, and left. The second day he came and did the same thing.
The third day he came and the salesman said, "Sorry, we don't have carrots. We only have cucumbers."
So the man bought two cucumbers and put one in each of his ears. The salesman had enough and asked, "Hey, how come you put those cucumbers in your ears?"
The man replied, "Because you didn't have any carrots."