import java.util.*;
/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
         Set<ListNode> set=new HashSet<>();
        while (pHead1!=null){
            set.add(pHead1);
            pHead1=pHead1.next;
        }
        while (pHead2!=null){
            if(set.contains(pHead2)){
                return pHead2;
            }
            pHead2=pHead2.next;
        }
        return null;

    }
}