Problem Statement  
A refactorable number is defined to be a number that is divisble by the number of distinct factors that it has. Examples of refactorable numbers include 1 (1 factor), 12 (6 factors), and 9 (3 factors), but not 7 (2 factors) or 16 (5 factors).
You will be given two ints, low and high. Return the number of refactorable numbers between low and high, inclusive.  
Definition  
 
Constraints  
  low will be between 1 and 2,000,000, inclusive.  
  high will be between low and 2,000,000, inclusive.  
Examples  
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