The school library buys back a batch of books. Each class is divided into 26 books. After distributing them to 18 classes, there are still 20 books left. How many books did the school buy back in total?
学校图书馆购回一批图书，每班分26本，分给18个班后，还剩20本，学校共购回多少本图书？
<gadget id="calculator">26 * 18</gadget>
<output>468</output>

<gadget id="calculator">468 + 20</gadget>
<output>488</output>

<result>488</result>