def get_movie_gross_value(movies, movie_name):
    """
    Query helper to find the gross value of a movie, if the movie exists in the Graph.
    :param movies: Dictionary (name of the movie --> Movie Node for the movie)
    :param movie_name: Name of the movie to get gross value of.
    :return: Gross value of the movie, if a node for it exists, else -1
    """
    if movie_name in movies:
        return movies[movie_name].gross_value
    return -1