A piece of rectangular paper, the longer side is 20 cm, cut off the largest square, what is the perimeter of the remaining small rectangle.
一张长方形纸片，较长的边为20厘米，剪去一个最大的正方形，余下的小长方形的周长是多少．
<gadget id="calculator">20 + 20</gadget>
<output>40</output>

<result>40</result>