static int findMergeNode(SinglyLinkedListNode head1, SinglyLinkedListNode head2) {
        Set<SinglyLinkedListNode> nodeSet = new HashSet<>();
        
        SinglyLinkedListNode currh1 = head1;
        SinglyLinkedListNode currh2 = head2;
        while(currh1 != null){
            nodeSet.add(currh1);
            currh1 = currh1.next;
        }
        
        while(currh2 != null){
            if(nodeSet.contains(currh2)){
                return currh2.data;
            }
            currh2 = currh2.next;
        }
        
        return -1;   
    }