A B C D E F G H I J K L M N O
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  1 └┴┴┴┴┴┴┴┴┴┴┴┴┴┘ 

[ 1]● ==> H8   [ 2]○ ==> H9   [ 3]● ==> I10  [ 4]○ ==> I8   [ 5]● ==> G10
[ 6]○ ==> F10  [ 7]● ==> J7   [ 8]○ ==> F9   [ 9]● ==> I9   [10]○ ==> F8
[11]● ==> F7   [12]○ ==> G7   [13]● ==> E9   [14]○ ==> E10  [15]● ==> J10
[16]○ ==> G8   [17]● ==> H7   [18]○ ==> D11  [19]● ==> C12  [20]○ ==> F11
[21]● ==> F12  [22]○ ==> G11  [23]● ==> E11  [24]○ ==> D9   [25]● ==> C8
[26]○ ==> G5   [27]● ==> G6   [28]○ ==> D8   [29]● ==> D10  [30]○ ==> C9