The weather forecast for a certain day in December 2013 in Beijing is -4°C to 5°C. What is the temperature difference (the difference between the highest temperature and the lowest temperature) in Beijing on this day?
北京市2013年12月某日的天气预报是-4℃～5℃，这一天北京的温差(最高气温与最低气温的差)是多少℃
<gadget id="calculator">5 - (-4)</gadget>
<output>9</output>

<result>9</result>