For parking in the parking lot, the charge is 2.5 yuan within 1 hour, and 2.50 yuan for every 0.5 hours beyond 1 hour. Driver Li paid a total of 12.50 yuan. How many hours did he park in total?
停车场停车，1小时内收费2.5元，超过1小时每0.5小时，收2.50元．李司机共交了12.50元，他一共停车几小时？
<gadget id="calculator">12.5 - 2.5</gadget>
<output>10</output>

<gadget id="calculator">10 / 2.5</gadget>
<output>4</output>

<gadget id="calculator">4 * 0.5</gadget>
<output>2</output>

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

<result>3</result>