void push(Stack *s, Node* newNode)
{
      Node* iterator;
      if(s->head == NULL)
      {
            s->head = newNode;
            s->tail = newNode;
            return;
      }
      iterator = s->head;
      while(iterator != tail)
      {
            iterator = iterator->next;
      }
      iterator->next = newNode;
      s->tail = iterator->next;
      return;
}