A train departs at 8:00 in the morning and arrives at 4:00 in the morning the next day. How many hours has it traveled in total?
一列火车早上8：00出发，第二天凌晨4：00到达，一共行了多少小时．
<gadget id="calculator">24 - 8</gadget>
<output>16</output>

<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<result>20</result>