Tie two wine bottles twice with a rope. The outer diameter of the wine bottle is 8 cm. The knot needs 15 cm of rope. How long is the rope in total?
用绳子将两个酒瓶捆两圈，酒瓶的外直径是8厘米，打结处打结处需要15厘米的绳子，一共需要多长的绳子？
<gadget id="calculator">3.14 * 8</gadget>
<output>25.12</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<gadget id="calculator">25.12 + 16</gadget>
<output>41.12</output>

<gadget id="calculator">41.12 + 15</gadget>
<output>56.12</output>

<result>56.12</result>