```
class Solution(object):
def addTwoNumbers(self, l1, l2):
"""
:type l1: ListNode
:type l2: ListNode
:rtype: ListNode
"""
list_1 = []
list_2 = []
while l1:
list_1.append(l1.val)
l1 = l1.next
while l2:
list_2.append(l2.val)
l2 = l2.next
return [int(i) for i in list(str(int(''.join([str(i) for i in list_1][::-1])) + int(''.join([str(i) for i in list_2[::-1]]))))][::-1]
```