请以JSON格式提供全球最畅销的三本书，必须包括书名、作者和销售数量，
user
{
    "books": [
        {
            "title": "Don Quixote",
            "author": "Miguel de Cervantes",
            "sales": "500 million"
        },
        {
            "title": "A Tale of Two Cities",
            "author": "Charles Dickens",
            "sales": "200 million"
        },
        {
            "title": "The Lord of the Rings",
            "author": "J.R.R. Tolkien",
            "sales": "150 million"
        }
    ]
}
assistant