Problem Statement  
Each character in maze will be '.' or 'X' denoting a free
square or an obstacle, respectively. Starting on some free square, and moving
exclusively through free squares, your goal is to leave the confines
of the maze through its left edge. Each move you make is either 'U', 'D', 'L', or
'R' denoting up, down, left, and right respectively. Moving upward
decreases which element of maze you are in, while moving
leftward decreases which character you are at in a particular
element. Nothing happens (your position does not change) if you move into an
obstacle, or try to leave the maze other than leftward. Similarly, nothing happens if you issue a move
and you have already left the maze (you already won).
Your friend has decided to challenge you by trying to solve the maze with the monitor off. This means you do not know which position you have started in or if you have won. Return the shortest sequence of moves that will solve the maze regardless of your initial position. If there are multiple shortest solutions, return the one that occurs first lexicographically. If there is no solution, return an empty string.  
Definition  
 
Constraints  
  maze contains between 1 and 5 elements, inclusive.  
  Each element of maze will contain between 1 and 4 characters, inclusive.  
  Each element of maze will contain the same number of characters.  
  Each character in maze will be '.' or 'X'.  
  maze will contain at least one '.'.  
Examples  
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