The folk song "wear leather jacket in the morning and wear gauze in the afternoon" vividly depicts the wonderful temperature changes in Xinjiang, my country. On a certain day in May in Urumqi, the highest temperature is 18°C and the lowest temperature is -2°C, what is the maximum temperature difference in that day?
"早穿皮袄午穿纱"这句民谣形象地描绘了我国新疆奇妙的气温变化象．乌鲁木齐五月的某一天，最高气温是18℃，最低温度是-2℃，则当天的最大温差是多少℃．
<gadget id="calculator">18 - (-2)</gadget>
<output>20</output>

<result>20</result>