Xiao Liang went to bed at 21:00 and got up at 6:00 the next day. How many hours did he sleep in total?
小亮21时睡觉，第二天6时起床，他一共睡了多少小时．
<gadget id="calculator">3 + 6</gadget>
<output>9</output>

<result>9</result>