*-----------*
|.9.|..5|..2|
|8.4|...|..6|
|.2.|..4|.7.|
|---+---+---|
|...|.1.|.69|
|..9|...|3..|
|68.|.3.|...|
|---+---+---|
|.6.|5..|.4.|
|9..|...|5.3|
|4..|2..|.1.|
*-----------*