A rectangular vegetable field is 24 meters long and 13 meters wide. There are guardrails around it. What is the length of the guardrails?
一个长方形菜地，长24米，宽13米，在四周围上护栏，护栏长多少米．
<gadget id="calculator">24 + 13</gadget>
<output>37</output>

<gadget id="calculator">37 * 2</gadget>
<output>74</output>

<result>74</result>