1000                                     

       1000                500         10                                     

   872              

⑴   500    1000 500    

⑵    750         500    500+500/2=500+250   

⑶   875          250    750+250/2=750+125   

⑷   812        125  0.5    875-63   

⑸  844          63  0.5    812+32   

⑹    860         32    844+16 

⑺    868           16    860+8   

⑻    872         8    868+4   

⑼   870   872    871 872         

            871         2    870+1 

                    872           

      100023                                                             

                                               