A square rug needs to be bordered by a lace. The side length of the carpet is 4 meters, what is the required lace length?
一块正方形地毯的四周需要镶一条花边．地毯的边长为4米，求所需花边长度？
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<result>16</result>