9                                                                                                                                                                                          

                                             
                                                                                                                                                                                                                                  

 
                                         
                                                                                                                                                                                                                                    40             40 90                    10                         5 6                                                                                                                                            
                              
                                                                                        
                                 
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            3 5                                                                   

                
                    
    1             20                           
   2                                           
   3                              

  
   
     
   4                                    
  5                                       
  6                                

  7                                        
  8                   

 
   
  9                                        
  10                                
  11                             
  12                             
 
  13                             
  14                                          
  15                                      
 
  
    
  16                                         
  17                                        
  18                                                     
       