Problem Statement  
A string composed of the letters 'A' and 'B' is called beautiful if it satisfies all of the following criteria:
Given countA, countB, maxA and maxB, return the maximum possible length of a beautiful string.  
Definition  
 
Constraints  
  countA will be between 0 and 1000000, inclusive.  
  countB will be between 0 and 1000000, inclusive.  
  maxA will be between 0 and 1000000, inclusive.  
  maxB will be between 0 and 1000000, inclusive.  
Examples  
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