Sudoku rules

- Sudoku is played over a 9x9 grid, divided to 3x3 sub grids called "regions":

- Sudoku begins with some of the grid cells already filled with numbers:

- The object of Sudoku is to fill the other empty cells with numbers between 1 and 9 (1 number only in each cell) according the following guidelines:

1. Number can appear only once on each row:

Allowed
Not allowed

2. Number can appear only once on each column:

Allowed		Not allowed

3. Number can appear only once on each region:

Allowed		Not allowed

- A summary of these guidelines would be, that a number should appear only once on each row, column and a region.