class Solution:
    def oddEvenList(self, head: ListNode) -> ListNode:

        if head is None or head.next is None:
            return head

        odd = head
        even = head.next
        evenHead = head.next

        while(even and even.next):
            odd.next = odd.next.next
            odd = odd.next

            even.next = even.next.next
            even = even.next

        odd.next = evenHead

        return head