# Print the plan with words.
	fun print_plan(plan: Sequence[Int])
	do
		var s = new Array[String]
		for i in plan do
			if i == -1 then
				s.add "right(>)"
			else if i == 1 then
				s.add "left(<)"
			else if i == -width then
				s.add "down(v)"
			else if i == width then
				s.add "up(^)"
			else
				abort
			end
		end
		print "Solution in {plan.length} moves: {s.join(" ")}"
	end