There are some popular science books in the book corner of Class 5 and 2. There are 2 books left in 3 books and 3 local books, 3 books left in 5 books and 5 local books, and 2 books left in 7 books and 7 local books. At least how many popular science books are there in the book corner of Class 5 and 2 ?
五2班的图书角有一些科普读物，3本3本地数剩2本，5本5本地数剩3本，7本7本地数剩2本，五2班的图书角至少有多少本科普读物？
<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<gadget id="calculator">21 + 2</gadget>
<output>23</output>

<result>23</result>