设计一个程序，其中有3个类，即CBank,BBank和GBank，分别为中国银行类，工商银行类和农业银行类。

每个类都包含一个私有数据balance，用于存放储户在该行的存款数，另有一个友元函数total用于计算储户在这3家银行中的总存款数。

-Design a program, of which there are three categories, namely CBank BBank and GBank Chinese bank, ICBC class, and the Agricultural Bank. Each class contains a private data balance is used to store the number of deposits of depositors in the bank, and another friend function total used to calculate the savers of the total deposits in three banks.