size: 3
----c----
--c-b-c--
c-b-a-b-c
--c-b-c--
----c----
size: 5
--------e--------
------e-d-e------
----e-d-c-d-e----
--e-d-c-b-c-d-e--
e-d-c-b-a-b-c-d-e
--e-d-c-b-c-d-e--
----e-d-c-d-e----
------e-d-e------
--------e--------
size: 15
----------------------------o----------------------------
--------------------------o-n-o--------------------------
------------------------o-n-m-n-o------------------------
----------------------o-n-m-l-m-n-o----------------------
--------------------o-n-m-l-k-l-m-n-o--------------------
------------------o-n-m-l-k-j-k-l-m-n-o------------------
----------------o-n-m-l-k-j-i-j-k-l-m-n-o----------------
--------------o-n-m-l-k-j-i-h-i-j-k-l-m-n-o--------------
------------o-n-m-l-k-j-i-h-g-h-i-j-k-l-m-n-o------------
----------o-n-m-l-k-j-i-h-g-f-g-h-i-j-k-l-m-n-o----------
--------o-n-m-l-k-j-i-h-g-f-e-f-g-h-i-j-k-l-m-n-o--------
------o-n-m-l-k-j-i-h-g-f-e-d-e-f-g-h-i-j-k-l-m-n-o------
----o-n-m-l-k-j-i-h-g-f-e-d-c-d-e-f-g-h-i-j-k-l-m-n-o----
--o-n-m-l-k-j-i-h-g-f-e-d-c-b-c-d-e-f-g-h-i-j-k-l-m-n-o--
o-n-m-l-k-j-i-h-g-f-e-d-c-b-a-b-c-d-e-f-g-h-i-j-k-l-m-n-o
--o-n-m-l-k-j-i-h-g-f-e-d-c-b-c-d-e-f-g-h-i-j-k-l-m-n-o--
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------o-n-m-l-k-j-i-h-g-f-e-d-e-f-g-h-i-j-k-l-m-n-o------
--------o-n-m-l-k-j-i-h-g-f-e-f-g-h-i-j-k-l-m-n-o--------
----------o-n-m-l-k-j-i-h-g-f-g-h-i-j-k-l-m-n-o----------
------------o-n-m-l-k-j-i-h-g-h-i-j-k-l-m-n-o------------
--------------o-n-m-l-k-j-i-h-i-j-k-l-m-n-o--------------
----------------o-n-m-l-k-j-i-j-k-l-m-n-o----------------
------------------o-n-m-l-k-j-k-l-m-n-o------------------
--------------------o-n-m-l-k-l-m-n-o--------------------
----------------------o-n-m-l-m-n-o----------------------
------------------------o-n-m-n-o------------------------
--------------------------o-n-o--------------------------
----------------------------o----------------------------