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

[ 1]● ==> H8   [ 2]○ ==> I9   [ 3]● ==> H6   [ 4]○ ==> J8   [ 5]● ==> I6
[ 6]○ ==> H9   [ 7]● ==> J6   [ 8]○ ==> G6   [ 9]● ==> G9   [10]○ ==> I7
[11]● ==> H7   [12]○ ==> J5   [13]● ==> H4   [14]○ ==> H5   [15]● ==> I5
[16]○ ==> K7   [17]● ==> L6   [18]○ ==> K6   [19]● ==> F8   [20]○ ==> G7
[21]● ==> I4   [22]○ ==> K9   [23]● ==> K8   --