A 7-meter-deep pit, a snail climbs up from the bottom of the pit, climbs up 3 meters during the day, and slides down 2 meters at night. Question: How many days will it take for this snail to climb out of this pit?
一个7米深的坑，一只蜗牛从坑底往上爬，白天爬上3米，晚上滑下2米．问：这只蜗牛几天能爬出这个坑？
<gadget id="calculator">7 - 3</gadget>
<output>4</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>