A duck walks into a bar, and asks, "Hey mister, do you have any duck food?"
The bartender says, "No, this is a bar. We don't have any duck food."
The duck leaves.
The next day, the duck comes back, and asks, "Hey mister, do you have any duck food?"
The bartender says, "NO! I told you, this is a bar, we don't have any duck food!"
The duck leaves.
The third day, the duck returns, "Hey mister, do you have any duck food?"
The bartender replies, "Look, I've told you twice, this is a bar, we have no duck food! If you come in here again asking for duck food, I'm going to nail your little webbed feet to the floor!"
The duck leaves.
On the fourth day, the duck returns, "Hey mister, do you have any nails?"
The bartender, obviously annoyed, yells in reply, "THIS IS A BAR!!! WHY WOULD WE HAVE NAILS?!?!?"
The duck asks, "Do you have any duck food?"