1                                  16                       25                         7               

  27                      20                               8                                                    31   

                                            30                                    22                                   

                     9                                 15                                              10              

                                        2                            29                                             23

        17                                                                              18                              

                             3                                     12                                                    

                                                       24                                                     4          

                     11                                                                   13                             

                                        5                                                                    6            

    19                  28                21                                 14                             26