.                                     
                       .. #                                  
                   .  ..    #                                
                   ##  .. . #                                
                     .  .  #                                 
                     ##..   #                                
                  . .#.  .  #.                               
                   .... ..# #.#                              
                  . . .... . .#                              
                  ..# #..  .#    ##                          
                      # .#...#. ..#                          
                     ##.... . .                              
                    .#.... .  .                              
                    ......#### #                             
                   ..#....z.4#.#                             
                   .###...z#...#                             
                      ##..####.#                             
                      ..#.   # #                             
                     ## . ∆   .#                             
                       ..      .                             
                      #.     # #                             
                      ##