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 
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Not allowed  |
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2. Number can appear only once on each column:
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Allowed |
Not allowed |
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3. Number can appear only once on each region:
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Allowed |
Not allowed |
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Allowed
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| Not allowed |
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- A summary of these guidelines would be, that a number should appear only once on each row, column and a region.