The school library has 50 bookshelves, each shelf has three floors, and each floor contains 20 books. How many books are there in the school library?
学校图书馆有50个书架，每个书架三层，每层放书20本，学校图书馆一共有图书多少本？
<gadget id="calculator">50 * 3 * 20</gadget>
<output>3_000</output>

<result>3_000</result>