% heyawake 21 by ?, http://www.janko.at/Raetsel/Heyawake/021.a.htm
heyawake
medium
10 10
+-------+---+-----+-+
|1......|...|.....|2|
+-+-----+...+---+-+.|
|.|2....|...|...|1|.|
|.+-+-+-+---+---+.|.|
|.|.|2|.........|.|.|
|.|.|.+-------+-+.|.|
|.|.|.|7......|.|.|.|
+-+-+.|.......|.+-+-+
|...|.|.......|.|...|
|...|.|.......|.|...|
|...|.|.......|.|...|
+-+-+.|.......|.+-+-+
|.|.|.|.......|.|.|.|
|.|.+-+-------+.|.|.|
|.|.|.........|.|.|.|
|.|.+---+---+-+-+-+.|
|.|.|...|...|.....|.|
|.+-+---+...+-----+-+
|.|.....|...|2......|
+-+-----+---+-------+
