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