Experimental Primary School has winter vacation on January 18th and starts on February 7th. How many days are there in total for this winter vacation?
实验小学1月18日放寒假，2月7日开学，这个寒假一共放了多少天？
<gadget id="calculator">31 - 18</gadget>
<output>13</output>

<gadget id="calculator">13 + 1 + 6</gadget>
<output>20</output>

<result>20</result>