The primary school holiday started on January 13, 2013, and school started on March 1. How many days did the winter vacation last?
小学在2013年1月13日开始放假，3月1日开学，寒假共放了多少天．
<gadget id="calculator">31 - 13</gadget>
<output>18</output>

<gadget id="calculator">18 + 1 + 28</gadget>
<output>47</output>

<result>47</result>