public class Homework4B
{ 
   /**
      Returns a solution to a puzzle.
      @param p a puzzle
      @return a solution or null if none exists
   */
   public static Puzzle solvePuzzle(Puzzle p)
   {
      // ...
      return null;
   }

   public static void main(String[] args) 
   {
      Puzzle p = new Puzzle("3A6", "36B", "71C");
      System.out.println(solvePuzzle(p));
   }
}