Grandma Li used a fence to surround a vegetable field with a length of 8 meters and a width of 5 meters. In order to save materials, one side was leaning against the wall to surround this vegetable field. How many meters of fence should be used at least?
李奶奶用篱笆围一块长8米，宽5米的菜地，为了节省材料，一面靠墙，围这块菜地，至少要用多少米的篱笆？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 8</gadget>
<output>18</output>

<result>18</result>