def sum_book_score(book_idx_list, book_score_list):
    """
    Helper function to get sum of book scores

    Args:
        book_idx_list: List of Book Index
        , book_score_list: List of Book Scores
    
    Returns:
        sum of book scores
    """
    return sum(book_score_list[book_idx] for book_idx in book_idx_list)