import java.util.HashMap;
public class Solution {
    HashMap<ListNode, Integer> map = new HashMap<>();

    public ListNode EntryNodeOfLoop(ListNode pHead)
    {
        ListNode p = pHead;
        while(p!=null){
            if(!map.containsKey(p)){
                map.put(p,1);
            }else{
                return p;
            }
            p = p.next;
        }
        return null;
    }
}