There hangs a big sign at the gas station:

“Whoever takes full tank can take part in the lottery. The prize is free sex.”

Two friends drive at the gas station, take full tank and ask to take part of the lottery.

“The rules are simple,” the gas station guy says. “I think a number from one to ten and you have to guess the number.”

“Seven!” says one man.

“Wrong! I was thinking of two.”

Two weeks later the men are back. One of them tries his luck again, supposing three.

“No luck again. I was thinking of five. Try again next time.”

Two friends drive away.

The one who guessed says to his mate:

“You know what I think? The guy is just a crook.”

“No, he’s not,” argues the other. “My wife won twice last week!”