On March 7, the weather forecast column in Harbin showed that the temperature was -5°C to 4°C. What is the temperature difference (that is, the difference between the highest temperature and the lowest temperature) of the day?
3月7日，哈尔滨的天气预报栏上显示，气温为-5℃～4℃．当天的温差(即最高气温与最低气温相差)是多少℃．
<gadget id="calculator">4 - (-5)</gadget>
<output>9</output>

<result>9</result>