Node n = n1;
		while (n != null) {
			n.setMark();
			n = n.parent;
		}

		// check for intersect moving up from n2
		// will unmark ancestor
		boolean haveMetAncestor = false;
		n = n2;
		while (n != null) {
			if (n.mark) {
				bLength++;
				haveMetAncestor = true;
			}
			if (!haveMetAncestor) {
				bLength++;
			} else {
				n.setMark();
			}
			n = n.parent;
		}

		// calculate distance from n1 to intersect, while unmarking.
		n = n1;
		while (n.mark) {
			aLength++;
			n = n.parent;
		}
		while (n != null) {
			n.setMark();
			n = n.parent;
		}