Problem Statement  
A prefixfree code of size N which uses K characters is a set of N distinct strings such that
You are given the size of the code N and the costs of using the characters characterCosts. Return the minimal possible cost of a prefixfree code of size N which uses these character costs.  
Definition  
 
Constraints  
  N will be between 2 and 500, inclusive.  
  characterCosts will contain between 2 and 50 elements, inclusive.  
  Each element of characterCosts will be between 1 and 100, inclusive.  
Examples  
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