*-----------*
|...|3..|5..|
|7.6|...|319|
|.3.|...|.7.|
|---+---+---|
|.64|..7|..8|
|...|9.4|...|
|2..|6..|75.|
|---+---+---|
|.7.|...|.8.|
|643|...|1.5|
|..9|..5|...|
*-----------*