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