import java.util.HashSet;
import java.util.Set;
/*
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 a = pHead1;
        ListNode b = pHead2;

        while(a != b){
            if(a == null){
                a = pHead2;
            }else{
                a = a.next;
            }

            if(b == null){
                b = pHead1;
            } else {
                b = b.next;
            }
        }
        return a;
    }
}