Linked list infinite loop c++

I've created two linked lists it's supposed to do a union and a merge. If I run the functions separately it does the task it's supposed to do merge or union. But when I try to output both simultaneously, the code infinitely keeps going. I don't know if it has to do with my null or the functions themselves.

#include <iostream>
using namespace std;

    struct Node{
    int num;
    Node *next;
    };

//

Node * unionLL (Node * LA, Node * LB)
{
 
      if(LA == NULL)
    {
         return LB;
    }
        if(LB == NULL)
        {
            return LA;
        }
        Node *temp = NULL;//Creation of a node name temp as a place holder
        if(LA != NULL) // if LA is less than LB
        {
             temp = LA;
             temp->next = unionLL(LA->next, LB);
        }
        else if(LB != NULL)
        {
            temp = LB;
            temp->next = unionLL(LA,LB->next);
        }
            return temp;
        
}


Node * mergeLL (Node * LA, Node * LB) // method
{
    if(LA == NULL)
    {
         return LB;
    }
        if(LB == NULL)
        {
            return LA;
        }
        Node *temp = NULL;//Creation of a node name temp as a place holder
        if(LA->num<=LB->num) // if LA is less than LB
        {
              temp = LA;
             temp->next = mergeLL(LA->next, LB);
        }
        else if(LB->num<=LA->num)
        {
            temp = LB;
            temp->next = mergeLL(LA,LB->next);
        }
            return temp;

}

int main()
{
 // set 1
    Node *head = new Node(); // Creation of node
    Node *neighbor1 = new Node();
    Node *neighbor2 = new Node();
    Node *neighbor3 = new Node();


    neighbor3->num=11;
    neighbor2->num=8;
    neighbor1->num=5;
    head->num= 3; // head is leading node

    head->next =neighbor1;
    neighbor1->next = neighbor2;
    neighbor2->next = neighbor3;
    neighbor3->next = NULL;

 // set 2

    Node *head2 = new Node(); // Creation of node
    Node *neighbor6 = new Node(); 
    Node *neighbor7 = new Node(); 
    Node *neighbor8 = new Node(); 
    Node *neighbor9 = new Node(); 
    Node *neighbor10 = new Node(); 

    head2->num= 2; // head is leading node
    neighbor6->num=6; // neighbor points to num which value is 6
    neighbor7->num=8;
    neighbor8->num=9;
    neighbor9->num=22;
    neighbor10->num=24;

    head2->next =neighbor6; //link to next element
    neighbor6->next = neighbor7; 
    neighbor7->next = neighbor8; 
    neighbor8->next = neighbor9; 
    neighbor9->next = neighbor10; 
    neighbor10->next = NULL; 

    Node *head3 = head;
    Node *head4 = head2;

    Node *Merge = mergeLL(head,head2);
    cout<<"mergeLL(LA, LB) = ";
    while(Merge != NULL)
    {
      cout<<Merge->num; cout<<" "; //end is no new line
      Merge= Merge->next;
    }




   Node *unionLLL = unionLL(head3,head4);
    cout<<"unionLLL(LA, LB) = ";
    while(unionLLL != NULL)
    {

      cout<<unionLLL->num; cout<< " ";
      unionLLL= unionLLL->next;
    }

    return 0;







}