exercises 1.25

#include <iostream>  
#include "Sales_item.h"   
using namespace std;  

int main()  
{  
   Sales_item total;
   if(cin>>total){
       Sales_item book;
       while(cin>>book){
           if(total.isbn()==book.isbn()){
               total+=book;
           }else{
               cout<<total<<endl;
               total=book;
           }
           
       }
       cout<<total<<endl;
   }else{
       cout<<"data error"<<endl;
       return -1;
   }  
  return 0;
}