string(257) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E6%8A%95%E5%85%A5%E4%B8%8E%E4%BA%A7%E5%87%BA%E6%AF%94%E5%80%BC%E7%9A%84%E8%AE%A1%E7%AE%97%E4%BE%8B%E9%A2%98 => Received HTTP code 403 from proxy after CONNECT"
投入与产出比值的计算例题
