There is a rectangular fish pond with a length of 50 meters and a width of 30 meters. If it is to be made into a square fish pond, how many square meters will the area be increased at least?
有一个长50米、宽30米的长方形鱼塘，如果要把它建成正方形鱼塘，面积至少增加多少平方米？
<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">50 * 20</gadget>
<output>1_000</output>

<result>1_000</result>