/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode* my_head = new ListNode(0);
        ListNode* cur = my_head;
        for(ListNode* left=head;left!=nullptr;)
        {
            ListNode* right=left;
            while(right && left->val == right->val)
            {
                right = right->next;
            }
            if(right == left->next)
            {
                cur->next = left;
                cur = left;
                cur->next = nullptr;
            }
            left = right;
        }
        return my_head->next;
    }
};