From a rectangle with a length of 7 cm and a width of 4 cm, cut out the largest square. What is the perimeter of this square?
在一个长7厘米、宽4厘米的长方形中，剪下一个最大的正方形，这个正方形的周长是多少．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<result>16</result>