The building where Mr. Li lives has 20 stairs on each floor. Mr. Li lives on the 15th floor. There was a power outage today. Mr. Li had to walk home from the stairs. How many stairs did Mr. Li walk from the first floor to his home?
李老师家住的那座楼房，每层有20阶楼梯，李老师家住15楼，今天停电，李老师只有从楼梯走回家，李老师从一楼到家共走了多少阶楼梯？
<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">14 * 20</gadget>
<output>280</output>

<result>280</result>