do 1                                                                                                                                                                                                                       
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
                                                                                                                                                   yes                                                                                                                                                                           no                                                                                                                                        
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
                                                                                                                                                   CASE 1                                                                                                                                                                        CASE 3                                                                                                                                    
                                                                                                                                                   CASE 2                                                                             success                                                                                    CASE 4                                                                                                                                    
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
                                                                                                            do b                                                                                                                                                                                                                                                                    do c                                                                                   
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
               yes                                                                                                                                                                          no                                                                                         yes                                                                                                                                                                           no    
                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
               CASE 1                                                                            success                                                                                    CASE 2                                                                                     CASE 3                                                                             success                                                                                    CASE 4