Problem Statement  
An overlapping concatenation of an ordered pair of Strings (A, B) is a String S such that A is a prefix of S and B is a suffix of S. A shortest overlapping concatenation (SOC) of (A, B) is an overlapping concatenation whose length is as small as possible. For example, if A is "cabab" and B is "ababc", the shortest overlapping concatenation is "cababc" (all quotes for clarity). You are given two Strings A and B, in which some of the characters are known and some are unknown. Each character in A and B will be a lowercase letter ('a'  'z') if it is known or '*' if it is unknown.
Assuming that each unknown character will be selected uniformly at random from the characters contained in alphabet, return the expected length of the shortest overlapping concatenation of A and B.  
Definition  
 
Constraints  
  alphabet will contain between 1 and 26 lowercase letters ('a'  'z'), inclusive.  
  The characters in alphabet will be distinct.  
  A and B will contain between 1 and 32 characters, inclusive.  
  A and B will contain the same number of characters.  
  Each character in A and B will either be contained in alphabet or it will be '*'.  
Examples  
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