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.
  87      32  
52          49
1      8      7
      7  4      
    9  3  1    
      1  8      
9      2      6
25          1  
  68      5    
** Moderate