### Sukaku

**Sukaku** (*"Suuji Kakure"*; also known as *"Pencilmark Sudoku"*) has 81 groups of digits in a **9 x 9** grid. Like a standard sudoku, the puzzle must be completed in such a way that each row, each column and each **3 x 3** box contains digits 1 through 9. Only the candidates shown in the grid can be used.

Task files have the extension *.**SUK**.