It takes Xiao Ming 15 seconds to go up one floor, how many seconds does it take to go from the first floor to the sixth floor.
小明上一层楼用15秒，从一楼到六楼，需要多少秒．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">15 * 5</gadget>
<output>75</output>

<result>75</result>