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]○ ==> J9
[11]● ==> H7   [12]○ ==> G7   [13]● ==> K7   [14]○ ==> L7   [15]● ==> I5
[16]○ ==> H4   [17]● ==> K9   [18]○ ==> J4   [19]● ==> J12  [20]○ ==> L8
[21]● ==> L10  [22]○ ==> M11  [23]● ==> K11  [24]○ ==> I13  [25]● ==> H10