In a building, there are 18 steps between the upper and lower floors. How many steps do you need to climb from the first floor to the sixth floor?
一幢楼房，相邻的上下两层之间都有18级台阶，从一楼到六楼，一共要爬多少级台阶．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">18 * 5</gadget>
<output>90</output>

<result>90</result>