A snail climbs up the wall of a well 19 meters deep. It climbs up 5 meters during the day and slides down 3 meters at night. At this speed, how many days can it climb to the mouth of the well?
一只蜗牛沿着19米深的井壁往上爬．它白天向上爬5米，到了夜里往下滑3米．照这样的速度，它第多少天能爬到井口．
<gadget id="calculator">19 - 5</gadget>
<output>14</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<result>8</result>