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()



                               No. 5
              
             ( No. 60 -    )
   
                         ________________ 20___ .
   
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   -                 No. 60
     No.           -+------------------------------     
                   +-----------------------  No. 60       No.                 
                +---------.--  -              .                   
                 -- .-  +------------- -        +--------------------     
                        .. 10  15  20__             51  52  No. No.      
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                1   2    3   4   5     6    7  8   9     10    11  12  13  14  15  16    17 
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   +------------------------------------------------------------------------------------------------------------+