The school is going to build a playground with a length of 200 meters and a width of 80 meters. For the safety of the children, a fence should be built around it. How long should the fence be?
学校要建一个长200米，宽80米的运动场，为了小朋友的安全，要在四周围上栅栏，请问需要做多长的栅栏？
<gadget id="calculator">200 + 80</gadget>
<output>280</output>

<gadget id="calculator">280 * 2</gadget>
<output>560</output>

<result>560</result>