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]● ==> J10  [ 4]○ ==> I9   [ 5]● ==> I8
[ 6]○ ==> G9   [ 7]● ==> J9   [ 8]○ ==> J8   [ 9]● ==> K10  [10]○ ==> L11
[11]● ==> K7   [12]○ ==> K9   [13]● ==> I7   [14]○ ==> H7   [15]● ==> I6
[16]○ ==> L8   [17]● ==> L7   [18]○ ==> K8   [19]● ==> K5   [20]○ ==> J6
[21]● ==> M8   [22]○ ==> J5   [23]● ==> M7   [24]○ ==> J7   [25]● ==> J4