# Definition for singly-linked list.

 class ListNode:

     def __init__(self, x):

         self.val = x

         self.next = None

 class Solution:

     def addTwoNumbers(self, l1, l2):

         """

         :type l1: ListNode

         :type l2: ListNode

         :rtype: ListNode

         """

         head = ListNode(0)

         cur = head

         m = 0

         while True:

             if l1 is not None:

                 a = l1.val

             else:

                 a = 0

             if l2 is not None:

                 b = l2.val

             else:

                 b = 0

             if l1 is None and l2 is None and m == 0:

                 return head.next

             else:

                 add = a + b + m

                 cur.next = ListNode(add % 10)

                 m = (a+b+m) // 10

                 cur = cur.next

             if l1 is not None:

                 l1 = l1.next

             if l2 is not None:

                 l2 = l2.next