https://purengom.com/2016/02/04/%ec%95%a0%ed%94%8c-%ec%9b%8c%ec%b9%98apple-watch%eb%a5%bc-%ea%b5%ac%ec%9e%85%ed%95%98%eb%8a%94-%ec%99%80%ec%a4%91%ec%97%90-%ea%b2%aa%ec%9d%80-%ec%9d%bc/