----------XX
--X-------XXX
--XX------XXXX
--XXX-----XXXX
--XXXX----XXXX
--XXXXX---XXXX
---XXXXX--XXXX
--XXXXX--XXXX
----XXXX--XXXX
-----XXX--XXX
------XX--XX
-----XXXXXXXXXX
----XXXXXXXXXXXXX
----XXXXXXXXXXXXX
----XXXXXXXXXXXXXX
-----XXXXXXXXXXXXX
------XXXXXXXXXXX
--------XXXXXXXX