A meeting starts on July 28 and ends on August 3. How many days does this meeting last?
一个会议从7月28日开始，8月3日结束，这个会议开了多少天．
<gadget id="calculator">31 - 28</gadget>
<output>3</output>

<gadget id="calculator">3 + 1 + 3</gadget>
<output>7</output>

<result>7</result>