/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
class Solution {
    public ListNode findFirstCommonNode(ListNode headA, ListNode headB) {
        ListNode l1 = headA;
        ListNode l2 = headB;

        while(l1 != l2) {
            l1 = (l1 == null) ? headB: l1.next;
            l2 = (l2 == null) ? headA : l2.next;
        }

        return l1;
    }
}