# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    # @params:
    # - list1: Optional[ListNode]
    # - list2: Optional[ListNode]
    # @return: Optional[ListNode]
    def mergeTwoLists(self, list1, list2):
        pass
