public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
		// Start typing your Java solution below
		// DO NOT write main() function
		NumList numList = new NumList();
		ListNode sumNode = null;
		boolean carry = false;
		while (l1 != null || l2 != null) {
			int sum = 0;
			if (l1 != null) {
				sum += l1.val;
			}
			if (l2 != null) {
				sum += l2.val;
			}

			if (carry) {
				sum++;
			}
			if (sum >= 10) {
				sum %= 10;
				System.out.println("sum=" + sum);
				carry = true;
			} else {
				carry = false;
			}
			sumNode = new ListNode(sum);
			numList.appendNode(sumNode);
			if (l1 != null)
				l1 = l1.next;
			if (l2 != null)
				l2 = l2.next;
		}
		if (carry) {
			sumNode = new ListNode(1);
			numList.appendNode(sumNode);
		}
		return numList.headNode;
	}