A quadrilateral playground, with 10 red flags on each side (all four corners must be inserted), how many red flags should be planted in total.
一个四边形操场，每边插10面红旗(四个角上都要插)，一共要插多少面红旗．
<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">40 - 4</gadget>
<output>36</output>

<result>36</result>