The Nanjing Yangtze River Bridge is divided into two layers, the upper layer is a road bridge, and the lower layer is a railway bridge. The total length of the railway bridge and the road bridge is 11270 meters, and the length of the railway bridge is 2270 meters longer than that of the road bridge. How long is the road bridge of the Nanjing Yangtze River Bridge?
南京长江大桥共分两层，上层是公路桥，下层是铁路桥．铁路桥和公路桥共长11270米，铁路桥比公路桥长2270米，南京长江大桥的公路桥长多少米．
<gadget id="calculator">11_270 - 2_270</gadget>
<output>9_000</output>

<gadget id="calculator">9_000 / 2</gadget>
<output>4_500</output>

<result>4_500</result>