Xiaohua goes upstairs, it takes 20 seconds for each floor, how many seconds does it take to go from the first floor to the fifth floor.
小华上楼，每一层楼需要20秒钟，从一楼到五楼要多少秒钟．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">4 * 20</gadget>
<output>80</output>

<result>80</result>