class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None
        self.head = None
        self.tail = None

    def add(self,item):
        if not isinstance(item,ListNode):
            item = ListNode(item)
        if self.head is None:
            self.head = item
        else:
            self.next = item
        self.tail = item

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:

        l3 = ListNode(0)
        l3.head = (l1.val + l2.val)%10
        y = (l1.val + l2.val)//10
        while(l1.next != None and l2.next != None):
            if(l1.val != None):
                l1.val = 0
            if(l2.val != None):
                l2.val = 0
            l1 = l1.next
            l2 = l2.next
            x = (l1.val + l2.val)%10 + y
            l3.add(x % 10)
            y = x//10
        return l3.next