A duck walks into a convenience store and walks up the counter. The duck asks, "Got any grapes?" "No," said the puzzled shopkeeper. The duck smiles and walks out the door. A little while later the duck returns and asks, "Got any grapes?" The shopkeeper replies, "No! Like I already told you 15 minutes ago, I don't have any grapes!" The duck smiles and walks out. A little while later the duck returns and again asks "Got any grapes?" The irate shopkeeper yells, "No! We didn't have any, we don't have any, and were not going to have any. If you come back in here again I'll nail your webbed feet to the floor!" The duck smiles and walks out. Later the  duck returns and asks the shopkeeper "Got any nails?" The clerk says "NO!" The duck replies, "Good! Got any grapes?"