(loop with tree-diff = (trees:reduce tree #'- :initial-value 0 :from-end t)
for start = 0 then (1+ x)
for x = (position 1 bitvector :start start)
(loop with tree-diff = (trees:reduce tree #'- :initial-value 0 :from-end t)
for start = 0 then (1+ x)
for x = (position 1 bitvector :start start)