/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode deleteDuplication(ListNode head) {
ListNode dummy=new ListNode(0);
dummy.next=head;
ListNode p=dummy;
while(p.next!=null){
ListNode q=p.next;
while(q!=null&&q.val==p.next.val)q=q.next;
if(p.next.next!=q)p.next=q;
else p=p.next;
}
return dummy.next;
}
}