A snail wants to climb a 9-meter-deep dry well. It climbs up 3 meters during the day and slides down 2 meters at night. How many days does it take for the snail to climb to the mouth of the well?
一只蜗牛要爬一口9米深的枯井，它白天向上爬3米，晚上下滑2米，第多少天蜗牛能爬到井口．
<gadget id="calculator">9 - 3</gadget>
<output>6</output>

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

<gadget id="calculator">6 / 1</gadget>
<output>6</output>

<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<result>7</result>