A                                                                                                                                   
                                 A                                                                                                                                   
                                 A                                                                                                                                   
                                 AA                                                                                                                                  
                                 A                                                                                                                                   
                                 AA                                                                                                                                  
                                 A                                                                        B                                                          
                                 A                                                                                                                                   
                                                                                                                                                                     
                                 A                                                                                                                                 CA
                                 AA                                                                                                                                  
                                 A                                                                   bb                                                              
                                 AA                                                                                                                                  
                                                                                                                                                                     
                                                                                                                                                               ccc   
                                                                                                                                                                     
                                                                                                                                                                     
                                      a