/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplication(ListNode* head) {
        ListNode* tou=new ListNode(0);
        tou->next=head;
        ListNode* d=tou;
        ListNode* p=head;
        while(p&&p->next)
        {
            if(d->next->val == p->next->val)
            {
                int val=d->next->val;
                while(p->next&&p->next->val==val) {p=p->next;}
                d->next=p->next;
                p=d->next;
            }
            else
            {
               // if(p->next==NULL) return d;
               d=p;
               p=p->next;

            }
        }

        return tou->next;
    }
};