Cut out the largest square from a rectangular piece of paper with a length of 7 cm and a width of 5 cm. What is the perimeter of this square in cm?
从一个长7厘米、宽5厘米的长方形纸片中，剪下一个最大的正方形，这个正方形的周长是多少厘米．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>