Grandma got on the train at 8 o'clock in the evening and got off the train at 5 o'clock the next morning. How many hours did grandma stay on the train?
奶奶晚上8时上火车，第二天早上5时下火车，奶奶在火车上呆了多少小时．
<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<result>9</result>