from typing import Optional
from utils import ListNode, list_to_linklist

def deleteDuplicates(head: Optional[ListNode]) -> Optional[ListNode]:
    lens = 0
    p = head
    while p:
        lens += 1
        p = p.next

    return lens

print(deleteDuplicates(list_to_linklist([1, 2, 3, 6, 8])))