Place flowerpots by the side of a square pool, and place 5 potted flowers on each side, at least how many potted flowers are needed.
在一个正方形水池边摆花盆，每一边都要摆5盆花，至少需要多少盆花．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">20 - 4</gadget>
<output>16</output>

<result>16</result>