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]● ==> J8   [ 4]○ ==> I8   [ 5]● ==> I7
[ 6]○ ==> H6   [ 7]● ==> J6   [ 8]○ ==> K5   [ 9]● ==> J7   [10]○ ==> J5
[11]● ==> J9   [12]○ ==> J10  [13]● ==> L7   [14]○ ==> K7   [15]● ==> K8
[16]○ ==> M6   [17]● ==> L9   [18]○ ==> M10  [19]● ==> L10  [20]○ ==> L8
[21]● ==> K9   [22]○ ==> M11  [23]● ==> M9   [24]○ ==> N9   [25]● ==> K11
[26]○ ==> J12  [27]● ==> J11