class Solution:
    # @param {ListNode} l1
    # @param {ListNode} l2
    # @return {ListNode}
    def addTwoNumbers(self, l1, l2):
        def listiter(l):
            cur = l
            while cur:
                yield cur.val
                cur = cur.next
        def list2num(l):
            s, coe = 0, 1
            for x in listiter(l):
                s += coe * x
                coe *= 10
            return s
        def num2list(n):
            x, n = n % 10, n // 10
            head = ListNode(x)
            cur = head
            while n > 0:
                x, n = n % 10, n // 10
                newNode = ListNode(x)
                cur.next = newNode
                cur = newNode
            return head

        n1, n2 = list2num(l1), list2num(l2)
        s = n1 + n2
        return num2list(s)