https://purengom.com/2010/11/02/iphone-4%ec%99%80-%eb%8c%80%ec%9a%b0%ec%9d%bc%eb%a0%89-%ed%99%a9%eb%8b%b9-%ec%84%9c%eb%b9%84%ec%8a%a4-%ec%b4%9d-%ec%a0%95%eb%a6%ac/