Node* interleave(Node* list1, Node* list2){
  // ******** WRITE YOUR CODE HERE ********
  Node *returnList = new Node();
  Node *temp = new Node();

  if(list2 == NULL){
    copy(list1, returnList);
    return returnList;
  }

  if(list1 == NULL){
    copy(list2, returnList);
    return returnList;
  }

  copy(list1, returnList);
  returnList->next=temp;
  while(list1->next != NULL && list2->next != NULL){
    copy(list2,temp);
    copy(list1->next, temp->next);
    list1=list1->next;
    list2=list2->next;
  }
  return returnList;
}