Parking lot regulations: 2.50 yuan for parking within 1 hour, and 2.50 yuan for every 0.5 hours for more than 1 hour. Uncle Li paid 12.5 yuan for parking. How many hours did he park in this parking lot?
停车场规定：停车时间在1小时内收费2.50元，超过1小时的，每0.5小时收费2.50元，李叔叔交了12.5元的停车费．他在这个停车场停车多少小时．
<gadget id="calculator">12.5 - 2.5</gadget>
<output>10</output>

<gadget id="calculator">2.5 / 0.5</gadget>
<output>5</output>

<gadget id="calculator">10 / 5</gadget>
<output>2</output>

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

<result>3</result>