To place flower pots on the edge of a pentagonal pool so that there are 5 pots on each side, at least how many potted flowers are needed.
要在一个五边形的水池边上摆花盆，使每边都有5盆，至少需要多少盆花．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<result>20</result>