There were two nuns.. 
  
  One of them was known as Sister

 Mathematical (SM), 
  
  and the other one was known as Sister

 Logical (SL) . 
  
  It is getting dark and they are still far away

 from the convent. 
 
 SM: Have you noticed that a man has been

 following us for 

  the past thirty-eight and a half minutes? I

 wonder what he wants. 
 
 SL: It's logical. He wants to rape us. 
 
 SM: Oh, no! At this rate he will reach us in 15

 minutes 

  at the most! What can we do? 

 
 SL: The only logical thing to do of course is

 to walk faster. 
 
 SM: It's not working. 

 
 SL: Of course it's not working. The man did

 the only 

  logical thing. He started to walk faster, too.

 
 
 SM: So, what shall we do? At this rate he will

 reach us in one minute. 
 
 SL: The only logical thing we can do is split.

 You go that way and I'll go this way. He

 cannot follow us both. 
  
  So the man decided to follow Sister Logical. 
 
 
 
 Sister Mathematical arrives at the convent

 and is 

  worried about what has happened to Sister

 Logical. 
  
  Then Sister Logical arrives.. 

 
 SM: Sister Logical! Thank God you are here! 

  Tell me what happened! 

 
 SL: The only logical thing happened. The

 man couldn't follow us both, so he followed

 me 
 
 SM: Yes, yes! But what happened then? 
 
 SL: The only logical thing happened. I

 started to run 

  as fast as I could and he started to run as

 fast as he could. 
 
 SM: And? 
 
 SL : The only logical thing happened. He

 reached me. 
 
 SM : Oh, dear! What did you do? 
 
 SL : The only logical thing to do. I lifted my

 dress up. 
 
 SM : Oh, Sister! What did the man do? 
 
 SL: The only logical thing to do. He pulled

 down his pants. 
 
  
  SM: Oh, no! What happened then? 
 
 SL : Isn't it logical, Sister? A nun with her

 dress up can run faster than a man with his

 pants down. 
  
  And for those of you who thought it would

 be dirty, 
  
  Say two Hail Marys!