Problem Statement  
Given a int[] numList, for each nonempty subset of numList, compute the average of its elements, then return the average of those averages.  
Definition  
 
Notes  
  The returned value must have an absolute or relative error less than 1e9.  
Constraints  
  numList will contain between 1 and 8 elements, inclusive.  
  All elements of numList will be between 1000 and 1000, inclusive.  
  All elements of numList will be distinct.  
Examples  
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