A rectangular piece of thick paper, 20 cm long and 15 cm wide. Cut it into the largest square, what is the circumference of the remaining part?
一张长方形厚纸，长20厘米，宽15厘米．把它剪成一个最大正方形，剩余部分的周长是多少厘米？
<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">15 + 5</gadget>
<output>20</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<result>40</result>