https://blog.faceutil.com/2017/04/25/android-market-version-checker-%ec%95%88%eb%93%9c%eb%a1%9c%ec%9d%b4%eb%93%9c-%eb%a7%88%ec%bc%93-%eb%b2%84%ec%a0%84-%ed%99%95%ec%9d%b8%ed%95%98%ea%b8%b0-%e3%81%ad/