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