For the convenience of transportation, the store bundles 4 bottles of beer together. The outer diameter of the beer bottles is 10 cm, and they are tied with a rope for a week. How long should the rope be at least?
商店为了搬运方便，把4瓶啤酒捆在一起，啤酒瓶的外直径为10厘米，用绳子捆一周，至少要用多长的绳子？
<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">3.14 * 10</gadget>
<output>31.4</output>

<gadget id="calculator">40 + 31.4</gadget>
<output>71.4</output>

<result>71.4</result>