The parking lot stipulates that each parking fee is 3 yuan and can be parked for 2 hours. From now on, the fee will be 2 yuan per hour, (less than 1 hour will be counted as 1 hour). Zhang Ming will pay 15 yuan when picking up the car. How many hours did Zhang Ming's car park in total?
停车场规定，每次停车收费3元，可停2小时．以后每小时收费2元，(不到1小时按1小时计算)张明领车时付费15元，张明的车共停了几小时？
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 2</gadget>
<output>8</output>

<result>8</result>