                      21                2 4 6 7 8 9 11 15 16 17 18 19 24 25 27 29 33 35 37 42 50  

  21                               112          21                     

        21               

     112                                                      21          21        

         26   28         1962        19             1978   20           21          

                 21      21            21                      