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export default function deleteDuplicates(    head: ListNode | null,): ListNode | null {    if (!head) return head;
    if (head.next && head.val === head.next.val) {        while (head.next && head.val === head.next.val) {            head = head.next;        }        return deleteDuplicates(head.next);    } else {        head.next = deleteDuplicates(head.next);        return head;    }}import { ListNode } from "../reverse-linked-list/ListNode.ts";