Use a rectangular paper with a length of 6 meters and a width of 3 meters to fold out the largest square. What is the perimeter of this square in meters?
用一个长6米，宽3米的长方形纸，折出一个最大的正方形，这个正方形的周长是多少米．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<result>12</result>