*-----------*
|.54|.1.|..7|
|8.9|..4|.3.|
|..2|...|...|
|---+---+---|
|3.8|...|.4.|
|...|.5.|...|
|.6.|...|3.1|
|---+---+---|
|...|...|2..|
|.7.|6..|4.3|
|4..|.9.|51.|
*-----------*