The holiday starts on August 10th, and classes begin on September 1st. How many days are the holidays?
假期从8月10日开始，9月1日上课，假期是多少天．
<gadget id="calculator">31 - 10</gadget>
<output>21</output>

<gadget id="calculator">21 + 1</gadget>
<output>22</output>

<result>22</result>