A man walks into a bar and says,
"Excuse me, I'd like a pint of beer."

The bartender serves the drink and says,
"That'll be four dollars."

The customer pulls out a twenty-dollar bill and hands it to the bartender.

"Sorry, sir," the bartender says,
"but I can't accept that."

The man pulls out a ten-dollar bill and the bartender rejects his money again.

"What's going on here?" the man asks.

Pointing to a neon sign, the bartender explains,
"This is a Singles Bar."