A policeman is doing his rounds at night when he sees a drunk man searching intensely for something under a brightly lit street lamp.
"Hello, what are you doing here?" he asks.
"I've lost my keys and can't find them," the drunk slurps.
So they both look for the key, but after 10 minutes it is clear: there is no key here.
"Are you sure you lost your key here?" the cop asks.
"Nah, I lost the key in the park, but there is no light there."