In a rectangle whose length is 50 centimeters and width is 40 centimeters, cut out the largest square and reduce the area by how many square centimeters.
在一个长是50厘米，宽是40厘米的长方形中，截取一个最大的正方形，面积比原来减少多少平方厘米．
<gadget id="calculator">50 * 40</gadget>
<output>2_000</output>

<gadget id="calculator">40 * 40</gadget>
<output>1_600</output>

<gadget id="calculator">2_000 - 1_600</gadget>
<output>400</output>

<result>400</result>