Seventeen!!

One day this lunatic man was jumping up and down on 
a manhole cover screaming at the top of his lungs, 
"Seventeen!! Seventeen!!" Intrigued by the man's insane 
behavior, another man walks
over to him and asks why he is doing that. The crazy
man responded, "It's a blast. You have to try it. Jump as high 
as you can and scream 'Seventeen!!' as loud as humanly possible.
You get such a rush. Try it." Reluctantly, the second man gets 
on the manhole cover and barely hops and says, "Seventeen?"
very timidly. The insane man says, "No, no, no. You're doing 
it wrong.  Jump higher. Yell louder." So, the second man begins
jumping a little higher and speaking louder than normal. 
Finally he says, "Hey, you know, I am getting a little bit of 
a rush.  Seventeen!! Seventeen!!" The man jumps higher and higher, 
screaming louder and louder. The first man, once the second had
jumped high enough, yanked the manhole cover out from under the 
second, causing him to fall to his death. The original man
replaced the cover and, once again, began jumping and screaming,
"Eighteen!! Eighteen!!"