SUDOKU

Write a number from 1 to 9 into each empty square in the grid so that every number from 1 to 9 appears exactly once in each horizontal row, each vertical column, and each 3×3 block.
9    8    6    
  1    6    8  
          1    4
8          7    
  5          2  
    7    4    6
2    7    3    
  6    5    1  
    1    3    9
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