Problem Statement  
We have a rectangular castle. The first floor is protected by some number of guards. We want to have at least one guard in each row and in each column. You are given a String[] castle. The jth character of the ith element of castle is either '.' (free cell) or uppercase 'X' (guard). Return the smallest number of additional guards we have to place in the castle to achieve our goal.  
Definition  
 
Constraints  
  castle will contain between 1 and 50 elements, inclusive.  
  Each element of castle will contain between 1 and 50 characters, inclusive.  
  All elements of castle will contain the same number of characters.  
  Each character of each element of castle will be either '.' or uppercase 'X'.  
Examples  
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