There is a batch of storybooks, whether there are 20 people or 30 people, there are only 2 books. What is the minimum number of storybooks in this batch?
有一批故事书，无论是20人分，还是30人分都少2本，这一批故事书最少有多少本．
<gadget id="calculator">2 * 5 * 2 * 3</gadget>
<output>60</output>

<gadget id="calculator">60 - 2</gadget>
<output>58</output>

<result>58</result>