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) {
// write code here
if(head==null)
return null;
ListNode p1 = head;
ListNode p2 = head.next;
while(p2!=null){
if(p1.val==p2.val){
p1.next=p2.next;
p2 = p2.next;
}else{
p1 = p2;
p2 = p2.next;
}
}
return head;
}
}