If there is lace around a square handkerchief with a side length of 6 decimeters, at least how many decimeters of lace are needed.
在一块边长是6分米的正方形手帕四周镶上花边，至少需要多少分米的花边．
<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<result>24</result>