local hailstone:
	swap [ over ]
	while < 1 dup:
		if % over 2:
			#odd
			++ * 3
		else:
			#even
			/ swap 2
		swap push-through rot dup
	drop

if = (name) :(main):
	local :h27 hailstone 27
	!. = 112 len h27
	!. = 27 h27! 0
	!. = 82 h27! 1
	!. = 41 h27! 2
	!. = 124 h27! 3
	!. = 8 h27! 108
	!. = 4 h27! 109
	!. = 2 h27! 110
	!. = 1 h27! 111

	local :max 0
	local :maxlen 0
	for i range 1 99999:
		dup len hailstone i
		if < maxlen:
			set :maxlen
			set :max i
		else:
			drop
	!print( "number: " to-str max ", length: " to-str maxlen )
else:
	@hailstone