snail crawls from the bottom of a dry well to the mouth of the well. It climbs up 110 cm during the day and slides down 40 cm at night. At the end of the day on the fifth day, the snail reaches the mouth of the well. How many centimeters is this dry well?
一只蜗牛从一个枯水井底面向井口处爬，白天向上爬110厘米，而夜晚向下滑40厘米，第5天白天结束时，蜗牛到达井口处．这个枯水井有多少厘米．
<gadget id="calculator">110 - 40</gadget>
<output>70</output>

<gadget id="calculator">70 * 4</gadget>
<output>280</output>

<gadget id="calculator">280 + 110</gadget>
<output>390</output>

<result>390</result>