input: from typing import List
  
  def generate_html_table(results: List[tuple]) -> str:
      """ Generates an HTML table from the given list of tuples.
      Each tuple contains information about a book: title, author, genre, and sales.
      >>> generate_html_table([('Harry Potter', 'J.K. Rowling', 'Fantasy', 12000000), ('The Lord of the Rings', 'J.R.R. Tolkien', 'Fantasy', 15000000)])
      '<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr><tr><td>Harry Potter</td><td>J.K. Rowling</td><td>Fantasy</td><td>12000000</td></tr><tr><td>The Lord of the Rings</td><td>J.R.R. Tolkien</td><td>Fantasy</td><td>15000000</td></tr></table>'
      """
output:     html = "<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>"
      for book in results:
          html += f"<tr><td>{book[0]}</td><td>{book[1]}</td><td>{book[2]}</td><td>{book[3]}</td></tr>"
      html += "</table>"
      return html