The charging standard of a certain parking lot is: 10 yuan within 1 hour; 8 yuan per 0.5 hours for the part exceeding 1 hour; 10 yuan for every 0.5 hours for the part exceeding 2 hours. Master Li parks in this parking lot, and the bus fare is 56 yuan. Then, how many hours should Master Li park at least?
某停车场的收费标准是：1小时内收10元；超过1小时部分，每0.5小时收8元；超过2小时部分，每0.5小时收10元．李师傅在这个停车场停车，公交费56元，那么，李师傅至少停车多少小时．
<gadget id="calculator">1 / 0.5</gadget>
<output>2</output>

<gadget id="calculator">2 * 8</gadget>
<output>16</output>

<gadget id="calculator">56 - 10 - 16</gadget>
<output>30</output>

<gadget id="calculator">30 / 10</gadget>
<output>3</output>

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

<gadget id="calculator">1.5 + 2</gadget>
<output>3.5</output>

<result>3.5</result>