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.
  96      43  
87          59
1      2      6
      2  6      
    3  9  6    
      3  7      
3      7      8
78          65
  59      37  
*** Hard