Put colorful flags around the square playground of the school, and put one at each of the four vertices. A total of 80 colored flags are inserted, and how many flags are inserted on each side on average.
在学校正方形的操场四周插彩旗，四个顶点都插一面，共插了80面彩旗，平均每边插了多少面．
<gadget id="calculator">80 / 4</gadget>
<output>20</output>

<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<result>21</result>