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  7      94  
  3          18
6      5      7
      8  3      
    6  2  7    
      4  7      
5      8      1
48          3  
  19      8    
*** Hard