A rectangular vegetable field is 8 meters long and 5 meters wide. One side is against a wall and three sides are surrounded by fences. How many meters of fences are needed at least?
一块长方形的菜地，长8米，宽5米，一面靠墙，三面围上篱笆，至少需要多少米篱笆？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

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

<result>18</result>