Read this sentence:

 FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS.
 

Now count the F's in that sentence. Count them ONLY ONCE: do not go back and count them again. See the answer below...
 
 
 
 
 
 
 
 
 
 
 
 

ANSWER:
There are six F's in the sentence.
A person of average intelligence finds three of them. If you spotted four, you're above average. If you got five, you can turn your nose at most anybody. If you caught six, you are a genius. There is no catch. Many people forget the "OF"s. The human brain tends to see them as V's and not F's. Pretty weird, huh?