Tightly bind three steel pipes with a diameter of 2 decimeters together, and the rope is only wound once. At least how many decimeters of rope is needed? (neglected at joints)
把3根直径都是2分米的钢管紧紧地捆扎在一起，绳子只绕一圈．至少需要绳子多少分米？(接头处忽略不计)
<gadget id="calculator">3.14 * 2</gadget>
<output>6.28</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">6.28 + 6</gadget>
<output>12.28</output>

<result>12.28</result>