3 3
2 _ _ _ 8 _ 7 _ 1
_ 5 _ _ _ _ _ _ _
_ _ 6 _ _ _ 2 _ 4
7 _ _ 1 2 _ _ _ _
_ 2 _ 5 _ 6 _ 3 _
_ _ _ _ 3 9 _ _ 8
8 _ 2 _ _ _ 9 _ _
_ _ _ _ _ _ _ 6 _
3 _ 4 _ 1 _ _ _ 2
              

The first line has width and height of the sudoku regions. The rest of the lines are each row in the sudoku, with numbers, or underscores for blanks.