A                                                            
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                 A to C
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                       C               
                              A to B                                                                                                                                                   
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                       condition?                                                      
                     B                                                                                                                                                                 
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                              B to E                                                                                                                                   D               
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                     E                                                                                                                                                                 
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                              E to G                                                                                                                                   F               
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                 F to G
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                                                                                       
                                                                                                                          G