1        2    3        4      5       
6      7    8                     
9                     10        
              11     12          
            13         14    15      
 16   17        18        19            20   
21      22                   23      
           24                
                25       26    27    
28        29      30      31             
         32            33        
    34                       
   35       36                   
 37             38               
        39          40    41         
  42              43    44       45      
          46                 
  47    48                  49       
       50    51                  
 52                 53           
            54               
                55           
         56                  
                         
   57