.---------.---------.---------.
| 3 8 9 | 6 4 5 | 2 1 7 |
| 4 6 1 | 9 2 7 | 5 3 8 |
| 7 5 2 | 3 1 8 | 9 6 4 |
:---------+---------+---------:
| 2 4 8 | 1 7 6 | 3 5 9 |
| 6 9 3 | 5 8 2 | 7 4 1 |
| 5 1 7 | 4 3 9 | 6 8 2 |
:---------+---------+---------:
| 8 3 5 | 7 9 1 | 4 2 6 |
| 9 2 6 | 8 5 4 | 1 7 3 |
| 1 7 4 | 2 6 3 | 8 9 5 |
'---------'---------'---------'