string(255) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E5%A4%8D%E6%95%B0%E4%B9%98%E9%99%A4%E6%B3%95%E7%9A%84%E5%9F%BA%E6%9C%AC%E8%A7%84%E5%BE%8B => Failed to connect to 14.18.46.51 port 38206: Connection refused"
复数乘除法的基本规律
