*-----------*
|1..|9.7|6..|
|..9|.5.|217|
|...|..1|.85|
|---+---+---|
|4.7|...|.6.|
|...|5.6|...|
|.1.|...|7.9|
|---+---+---|
|79.|3..|...|
|581|.9.|3..|
|..3|7.5|..1|
*-----------*