Cut the largest square out of a rectangular cardboard with a length of 45 cm and a width of 20 cm. What is the remaining shape? What is its circumference?
从一个长45厘米，宽20厘米的长方形的纸板上剪下一个最大的正方形，剩下的是什么形？它的周长是多少？
<gadget id="calculator">45 - 20</gadget>
<output>25</output>

<gadget id="calculator">25 + 20</gadget>
<output>45</output>

<gadget id="calculator">45 * 2</gadget>
<output>90</output>

<result>90</result>