snail climbs up a well 10 meters deep, climbs up 5 meters during the day, and slides down 2 meters at night when it rests, how many days does it take to climb out of the well?
一只蜗牛从10米深的井中向上爬，白天爬上5米，晚上休息又滑下2米，它需要多少天才能爬出井口．
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

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

<result>4</result>