https://purengom.com/2010/12/28/ipad-%ec%88%98%eb%a6%ac-%ec%a7%84%ec%a7%9c-%ec%9e%ac%ec%95%99%ec%9d%80-%ec%97%ac%ea%b8%b0-%ec%9e%88%ec%97%88%eb%8b%a4-2-%ec%88%98%eb%a6%ac%eb%b9%84-59%eb%a7%8c-9%ec%b2%9c%ec%9b%90/