Hope Primary School will start summer vacation on July 15th and start school on August 23rd. How many days are there in this summer vacation?
希望小学7月15日起放暑假，8月23日开学，这个暑假一共多少天．
<gadget id="calculator">31 - 15</gadget>
<output>16</output>

<gadget id="calculator">16 + 1 + 22</gadget>
<output>39</output>

<result>39</result>