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