public class Solution {
    public ListNode deleteDuplication(ListNode head) {
        ListNode newhead = new ListNode(-1);
        ListNode temp = newhead;
        ListNode cur = head;
        while(cur != null){
            if(cur.next != null && cur.val == cur.next.val){
                while(cur.next != null && cur.val == cur.next.val){
                    cur = cur.next;
                }
                cur = cur.next;
            }
            else{
                temp.next = cur;
                temp = temp.next;
                cur = cur.next;
            }
        }
        temp.next = null;
        return newhead.next;
    }
}