def METHOD_NAME(l1, l2):
    dummy = ListNode(0)
    tail = dummy
    while l1 and l2:
        if l1.val <= l2.val:
            tail.next = l1
            l1 = l1.next
        else:
            tail.next = l2
            l2 = l2.next
        tail = tail.next
    tail.next = l1 or l2
    return dummy.next