编写程序，读入几个具有相同ISBN的交易，输出所有的读入交易的和，关键是如何控制读入的信息条数，假设我就读入两条信息，就要输出结果，亦或是三条

#include<iostream>
#include"Sales_item.h"
int main()
{
    Sales_item total,book;
    std::cout<<"enter some transactions:"<<std::endl;
    if(std::cin>>total)
    {
        while(std::cin>>book)
        {

            if(total.same_isbn(book))
            {
                total+=book;
            }
            else
            {
                std::cout<<"have different isbn"<<std::endl;
                return 1;
            }
        }
        std::cout<<"ISBN,number of copies sold,"
            <<"total revenue,and average price are:"
            <<std::endl<<total;
    }
    else
    {
        std::cout<<"no data"<<std::endl;
         return -1;
    }
return 0;

}