A duck goes into a grocery store and asks the grocer if he sells duck food.

The grocer says, "We don't sell duck food here."

The duck comes back the next day and asks the grocer if he sells duck food.

"I told you," he exclaims, "we don't sell duck food here!"

The duck leaves and comes back the next day. "Got any duck food?"

The grocer says, "Look duck, I told you, we don't sell duck food and if
you come back one more time, I am going to nail your little webbed feet
to the floor."

The duck leaves and comes back the next day. He asks the grocer, "Got
any nails?"

"No." the grocer replies.

"Good, got any duck food?"