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