Use an iron wire to tightly bind four pipes with a radius of 6 decimeters (not counting the joints), how many decimeters of iron wire are needed at least?
用一根铁丝将4根半径6分米的管子紧紧捆住(接头处不计)，至少需要多少分米铁丝？
<gadget id="calculator">3.14 * 2 * 1</gadget>
<output>6.28</output>

<gadget id="calculator">2 * 1 * 4</gadget>
<output>8</output>

<gadget id="calculator">6.28 + 8</gadget>
<output>14.28</output>

<result>14.28</result>