A building is 20 stories high, and there are 15 steps on two adjacent floors. How many steps does a person need to walk from the 1st floor to the 15th floor?
一幢楼房20层高，相邻两层有15级台阶，某人从1层到15层，要走多少级台阶．
<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">15 * 14</gadget>
<output>210</output>

<result>210</result>