small road is 100 meters long. From the beginning to the end of the road, there is a small flag every 4 meters on one side of the road. Now it is changed to have a flag every 5 meters. How many small flags should be pulled up?
一条小路长100米，从路的起点到终点，在路的一侧每隔4米插有一面小旗，现在要改成每隔5米插有一面旗，问要拔起多少面小旗？
<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<gadget id="calculator">100 / 20</gadget>
<output>5</output>

<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">1 - 6</gadget>
<output>-5</output>

<gadget id="calculator">25 + (-5)</gadget>
<output>20</output>

<result>20</result>