The school has 4 floors, and there are 15 steps between every two floors. How many steps are there in total?
学校有4层楼，每两层之间有15级台阶，一共有多少级台阶？
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<result>45</result>