import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param head ListNode类 
     * @return ListNode类
     */
    public ListNode deleteDuplicates (ListNode head) {
        if(head==null) return null;
        ListNode cur=head;
        while(cur!=null){
            if(cur.next!=null&&cur.val==cur.next.val){
                cur.next=cur.next.next;
                continue;
            }
            cur=cur.next;
        }
        return head;
    }
}