/**

 * Definition for singly-linked list.

 * function ListNode(val) {

 *     this.val = val;

 *     this.next = null;

 * }

 */

/**

 * @param {ListNode} l1

 * @param {ListNode} l2

 * @return {ListNode}

 */

var addTwoNumbers = function(l1, l2) {

    var head = new ListNode(0);

    var temp1 = 0;

    var temp2 = 0;

    var val1;

    var val2;

    while(l1 || l2 || temp1) {

        if (l1)val1 = l1.val;

        else val1 = 0;

        if (l2) val2 = l2.val;

        else val2 = 0;

        temp2 = Math.floor((val1 + val2 + temp1) % 10);

        temp1 = Math.floor((val1 + val2 + temp1) / 10);

        head.val += 1;

        var newNode = new ListNode(temp2);

        if(head.next == null){

            head.next = newNode;

        }

        else {

            var tempNode = head.next;

            while(tempNode.next != null)

                tempNode = tempNode.next;

            tempNode.next = newNode;

        }

        if (l1)l1 = l1.next;

        if (l2)l2 = l2.next;

    }

    return head.next;

};