There is a batch of books. After 30 students hold 26 books each, there are 39 books left. How many books are there in total?
有一批书，30个同学每人抱26本后，还剩39本，这批书共多少本？
<gadget id="calculator">26 * 30</gadget>
<output>780</output>

<gadget id="calculator">780 + 39</gadget>
<output>819</output>

<result>819</result>