https://purengom.com/2011/08/15/%ed%91%b8%eb%a5%b8%ea%b3%b0%ec%9d%b4-%ec%b6%94%ec%b2%9c%ed%95%98%eb%8a%94-ipad%ec%97%90-%ec%84%a4%ec%b9%98%ed%95%b4%eb%b3%bc%eb%a7%8c%ed%95%9c-%ec%95%b1/