A snail climbs an 8-meter-high wall, climbs up 4 meters during the day, and slides down 3 meters at night. After how many days, the snail climbs to the top of the wall.
一只蜗牛爬8米高的墙，白天向上爬4米，夜晚下滑3米，多少天后蜗牛爬到墙顶．
<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">4 - 3</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>