The charging standard of a certain parking lot is as follows: within 1 hour (including 1 hour), the fee is 2.5 yuan; for more than 1 hour, the fee is 1.5 yuan for every 0.5 hours (less than 0.5 hours, the fee is 0.5 hours). Uncle Li pays 8.5 yuan for parking. Do you know how long he parked?
某停车场收费标准如下：1小时内(含1小时)收费2.5元；超过1小时，每0.5小时收费1.5元(不足0.5小时，按0.5小时收费)．李叔叔交停车费8.5元，你知道他停车多久吗？
<gadget id="calculator">8.5 - 2.5</gadget>
<output>6</output>

<gadget id="calculator">1.5 / 0.5</gadget>
<output>3</output>

<gadget id="calculator">6 / 3</gadget>
<output>2</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>