A frog climbs up from the bottom of a 19-meter-deep well, climbs 3 meters during the day, and slides 2 meters at night. How many days does it climb out of the well?
一只青蛙从19米深的井底往上爬，白天爬3米，晚上下滑2米，第多少天爬出井口．
<gadget id="calculator">19 - 3</gadget>
<output>16</output>

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

<gadget id="calculator">16 / 1</gadget>
<output>16</output>

<gadget id="calculator">16 + 1</gadget>
<output>17</output>

<result>17</result>