定义四个接口，其方法协议分别

完成两个数的加法、减法、乘法和除法操作，其中加法接口是一

个父接口，并依次派生出其他接口。大家帮忙看一下。谢谢！

-4 interface definition, the methodology two agreements were completed several Adders, subtraction, multiplication and division operations. Adder interface which is a father interface, and were derived from other interfaces. We look at the help. Thank you!