Two young men were picked up by the police for smoking dope,
and they had to appear in court on a Friday before the judge.
The judge said, "You seem like nice young men, and seem to
have had no prior difficulties with the law, so I'm willing to
give you a second chance.  Rather than jail time.  I want each of you to
go out this weekend and try to show others the evils of drug use and 
get them to give up drugs forever.  I'll see you back in court on
Monday."

Monday, the two guys were back before the judge and he asked
the first young man,  "Well, how did you do over the weekend".
The young man replied, "Your honor, I persuaded 17 people to
give up drugs forever."
"17 people? That's wonderful! What did you tell them?"  "I
used a diagram your honor. I drew two circles like this:"
         
  ()         o

"I told them that this, (the big circle), is your brain before
drugs, and this, (the small circle), is your brain
after drugs."  "That's admirable! Replied the judge..
To the second boy the judge said, "And you, how did you do?"
"Well your honor, I persuaded 156 people to give up drugs
forever."
"156 people? That's just amazing! How did you manage that?"
"Well," replied the guy, "I used a similar approach. I too
drew two circles...
          
  ()         o

...and said, (pointing to the smaller circle), this is your
asshole before prison..."