A rectangular vegetable field is 8 meters long and 5 meters wide. How many meters does it take to walk around the vegetable field?
一块长方形菜地长8米，宽5米，绕菜地走一圈，要走多少米．
<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">2 * 13</gadget>
<output>26</output>

<result>26</result>