n = 20

mindepth = 4

maxdepth = mindepth + 2

if (maxdepth < n): maxdepth = n.

new_tree = class (item, depth):

/item = item

if (depth > 0):

i = item + item, depth--

/left = new_tree (i - 1, depth)

/right = new_tree (i, depth).

.

item_check = (tree):

if (tree /left):

tree /item + item_check (tree /left) - item_check (tree /right).

else:

tree /item.

.

stretch_depth = maxdepth + 1

check = item_check(new_tree(0, stretch_depth))

("stretch tree of depth ", stretch_depth,

"\t check: ", check, "\n") join print

longlivedtree = new_tree(0, maxdepth)

depth = mindepth, while (depth <= maxdepth):

iter = 1 << (maxdepth - depth + mindepth)

check = 0

i = 1

while (i <= iter):

check = check + item_check(new_tree(1, depth)) +

item_check(new_tree(-1, depth))

i++.

(iter * 2, "\t trees of depth ", depth,

"\t check: ", check, "\n") join print

depth = depth + 2.

("long lived tree of depth ", maxdepth, "\t check: ",

item_check(longlivedtree), "\n") join print