class Solution {
public:
ListNode deleteDuplicates(ListNode head) {
if(!head || !head->next)
return head;
ListNode* p = head;

    while(p->next){
        if(p->val == p->next->val)
            p->next = p->next->next;
        else
            p = p->next;
    }
    return head;
}

};