While the cashier was ringing up her purchases, the drunk calmly stated, "You must be single."
The woman was a bit startled by this proclamation, but she was intrigued by the derelict's intuition, since she was indeed single. She looked at her six items on the belt and saw nothing particularly unusual about her selections that could have tipped off the drunk to her marital status. Curiosity getting the better of her, she said "Well, you know what, you're absolutely correct. But how on earth did you know that?"
The drunk replied, "'Cause you're ugly."