class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        if (head == NULL) return head;
        ListNode* retHead = new ListNode;
        retHead->next = head;
        ListNode* p = retHead;
        while (p != NULL && p->next != NULL) {
            while (p->next != NULL && p->next->val == val)
                p->next = p->next->next;
            p = p->next;
        }
        return retHead->next;

    }
};