Cut the largest square out of a piece of rectangular paper with a length of 25 cm and a width of 20 cm. What is the perimeter of this square in cm?
在一张长25cm，宽20cm的长方形纸上剪下一个最大的正方形，这个正方形的周长是多少cm．
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>