*-----------*
|2..|7.4|.8.|
|8..|.2.|.6.|
|...|...|7..|
|---+---+---|
|...|.75|84.|
|4..|2.1|..7|
|.37|49.|...|
|---+---+---|
|..4|...|...|
|.9.|.6.|..1|
|.8.|5.7|..2|
*-----------*