n_append([a, b, c], [d, e], [a, b, c, d, e])
	n_append([b, c], [d, e], [b, c, d, e])
		n_append([c], [d, e], [c, d, e])
			n_append([], [d, e], [d, e])
n_length([a, b, c, d, e], 5)
	n_length([b, c, d, e], 4)
		n_length([c, d, e], 3)
			n_length([d, e], 2)
				n_length([e], 1)
					n_length([], 0)
n_isort([4, 2, 5, 3, 1], [1, 2, 3, 4, 5])
	n_isort([2, 5, 3, 1], [1, 2, 3, 5])
		n_isort([5, 3, 1], [1, 3, 5])
			n_isort([3, 1], [1, 3])
				n_isort([1], [1])
					n_isort([], [])
					n_insert(1, [], [1])
				n_insert(3, [1], [1, 3])
					n_insert(3, [], [3])
			n_insert(5, [1, 3], [1, 3, 5])
				n_insert(5, [3], [3, 5])
					n_insert(5, [], [5])
		n_insert(2, [1, 3, 5], [1, 2, 3, 5])
			n_insert(2, [3, 5], [2, 3, 5])
	n_insert(4, [1, 2, 3, 5], [1, 2, 3, 4, 5])
		n_insert(4, [2, 3, 5], [2, 3, 4, 5])
			n_insert(4, [3, 5], [3, 4, 5])
				n_insert(4, [5], [4, 5])