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) {
        ListNode p1=pHead1, p2=pHead2;        
        while(p1!=null || p2!=null){//同时结束(等于null时)
            if(p1 == p2){//找到了公共节点
                return p1;
            }
            p1 = (p1 == null)?pHead2:p1.next;
            p2 = (p2 == null)?pHead1:p2.next;
        }
        return null;
    }
}