The summer vacation is on July 11, and school starts on September 1. How many days are there in total?
7月11日放暑假，9月1日开学，假期共有多少天．
<gadget id="calculator">31 - 11</gadget>
<output>20</output>

<gadget id="calculator">20 + 1 + 31</gadget>
<output>52</output>

<result>52</result>