A square with a side length of 3 decimeters is exactly surrounded by a piece of iron wire. What is the length of this wire in decimeters?
用一根铁丝正好围成一个边长为3分米的正方形，这根铁丝长多少分米．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<result>12</result>