How many days does Xiaoqiang participate in the summer camp from July 15th to August 12th?
小强参加夏令营活动，从7月15日到8月12日，一共有多少天．
<gadget id="calculator">31 - 15</gadget>
<output>16</output>

<gadget id="calculator">16 + 1</gadget>
<output>17</output>

<gadget id="calculator">17 + 12</gadget>
<output>29</output>

<result>29</result>