 15
                            
                                        15              
                            
                            
                     
                                                 20              
                            
                                        3D ture
                            
                                        20              
                            
                                        3D ture
                            
                     
                                                 18
                            
                                        18              
                            
                            
                     
                                                 9
                            
                                        9               
                            
                            
                    