# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
from typing import Optional

from base.linked_list.ListNode import ListNode


class Solution:
    # TODO
    def reverseEvenLengthGroups(self, head: Optional[ListNode]) -> Optional[ListNode]:
        pass