a,b1                                                                            
?Redo from start                                                                
a,ba                                                                            
?Redo from start                                                                
a,ba,b                                                                          
?Redo from start                                                                
a,b1,2,3                                                                        
?Redo from start                                                                
a,b                                                                             
?Redo from start                                                                
a,b1,2                                                                          
 1            2                                                                 
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
                                                                                
