There are 333 books on a three-story bookshelf, the second and third floors from bottom to top are 10 books less than the lower one, how many books are placed on the top one.
一个三层书架上放了333本书，从下向上第二、三层都比它的下一层少10本书，最上面一层放了多少本书．
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">333 - 10 - 20</gadget>
<output>303</output>

<gadget id="calculator">303 / 3</gadget>
<output>101</output>

<result>101</result>