Uncle Zhang surrounds a rectangular vegetable field with a length of 10 meters and a width of 5 meters by the wall. One side of the vegetable field is against the wall. How much fence should be used at least? (Think about it: Which side is better to put against the wall?)
张大伯在墙边围一块长10米，宽5米的长方形菜地，菜地一面靠墙，至少要用多少篱笆？(想一想：把哪条边靠墙比较好？)
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 10</gadget>
<output>20</output>

<result>20</result>