Remove Duplicates from Sorted List

public class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head==null|| head.next==null) return head;
        ListNode h = new ListNode(-1);
        h.next = head;
        ListNode l1 = head;
        ListNode l2 = l1.next;
        while(l2!=null){
            while(l2!=null && l1.val==l2.val){
                l2 = l2.next;
            }
            l1.next = l2;
            l1=l1.next;
        }
        return h.next;
    }
}