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]● ==> J6   [ 4]○ ==> G9   [ 5]● ==> J8
[ 6]○ ==> H9   [ 7]● ==> J9   [ 8]○ ==> J7   [ 9]● ==> H6   [10]○ ==> I7
[11]● ==> I8   [12]○ ==> K8   [13]● ==> H7   [14]○ ==> G6   [15]● ==> G8
[16]○ ==> F8   [17]● ==> F9   [18]○ ==> I6   [19]● ==> H5   [20]○ ==> H4
[21]● ==> D7   [22]○ ==> E7   [23]● ==> D6   [24]○ ==> D8   [25]● ==> E5
[26]○ ==> F4   [27]● ==> F6   [28]○ ==> D4   [29]● ==> E4   [30]○ ==> C6