A batch of books is packaged into 12 books per pack, 11 books are left, 18 books per pack, and 1 book is missing at the end, 15 books per pack, and 14 books are left at the end. How many books are there at least in this batch?
一批书，包装成每包12本，剩下11本，每包18本，最后还缺1本，每包15本，最后剩下14本．这批书至少有多少本？
<gadget id="calculator">2 * 2 * 3 * 3 * 3 * 5</gadget>
<output>540</output>

<gadget id="calculator">540 - 1</gadget>
<output>539</output>

<result>539</result>