A square flower bed has a perimeter of 84 meters. Do you know the area occupied by this flower bed?
一个正方形花坛，它的周长是84米，你知道这个花坛的占地面积吗？
<gadget id="calculator">84 / 4</gadget>
<output>21</output>

<gadget id="calculator">21 * 21</gadget>
<output>441</output>

<result>441</result>