#         self.next = None

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        
        len1, len2 = self.length(l1), self.length(l2)
        
        if len1>len2:
            l2 = self.pad(l2, len1-len2)
        else:
            l1 = self.pad(l1, len2-len1)