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

        dummy_head = ListNode(0)
        p, q, curr = l1, l2, dummy_head
        carry = 0
        while p or q:
            x = p.val if p else 0
            y = q.val if q else 0
            s = x + y + carry
            carry = s // 10
            s = s % 10
            curr.next = ListNode(s)
            curr = curr.next
            p = p.next if p else p
            q = q.next if q else q
        if carry:
            curr.next = ListNode(carry)
        return dummy_head.next