There is a tall building. It takes Xiaohong 1.5 minutes to go up one floor, and half a minute to go down one floor. She started to go up from the bottom floor at 8:45 in the morning, and went down immediately after reaching the highest floor. Don't stop there, return to the ground floor for the first time at 9:17 in the morning, how many floors does this building have?
有一座高楼，小红每登上一层需要1.5分钟，每下走一层需要半分钟，她从上午8：45开始不停地从底层往上走，到了最高层后立即往下走，中途也不停留，上午9：17第一次返回底层，则这座楼共有多少层．
<gadget id="calculator">15 + 17</gadget>
<output>32</output>

<gadget id="calculator">1.5 + 0.5</gadget>
<output>2</output>

<gadget id="calculator">32 / 2</gadget>
<output>16</output>

<gadget id="calculator">16 + 1</gadget>
<output>17</output>

<result>17</result>