A building has 12 floors, and each floor has 21 steps. Uncle Zhang walks from the first floor to the ninth floor to find friends. How many steps does he have to walk in total?
某大楼有12层，每层要走21台阶，张大叔从一楼到9楼找朋友，他一共要走多少个人台阶？
<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">21 * 8</gadget>
<output>168</output>

<result>168</result>