https://purengom.com/2017/11/03/%ed%81%b4%eb%a1%9c%eb%b0%94-ai-%ec%8a%a4%ed%94%bc%ec%bb%a4-%ed%94%84%eb%a0%8c%ec%a6%88-%eb%b8%8c%eb%9d%bc%ec%9a%b4%ec%9d%b4-%ec%99%94%ec%8a%b5%eb%8b%88%eb%8b%a4/