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.
      6    8    
  9    2    6  
    7    4    2
1    5    7    
  3    4    9  
    8          4
4    9          
  6    3    5  
    1    2    3
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