3 Doctors in Heaven

Three doctors were trying to get through the pearly gates.  The first, 
a pediatrician was warmly welcomed.  The second, a cancer specialist, 
was similarly received.  
     
"What do you do?" Saint Peter asked the third.
     
"I work for an HMO," the doctor said.  
     
Saint Peter tapped something into his computer, then looked up.   
"Okay," he said, "you can come in, but you have to leave after three days."