// AddSalesItemsSecure.cpp

#include <iostream>
#include "SalesItem.h"

using namespace std;

// SalesItem addition

SalesItem operator+( const SalesItem& aLeft, const SalesItem& aRight )
{
  SalesItem Result( aLeft );
  
  Result += aRight;
  return Result; // return by value
}

int main()
{
  SalesItem lItem1, lItem2;

  // read items
  cin >> lItem1 >> lItem2;

  // security check
  if ( lItem1.hasSameISBN( lItem2 ) )
    {
      // write item data
      cout << lItem1 + lItem2 << endl;
      return 0;
    }
  else
    {
      cerr << "Error, data must refer to same ISBN!" << endl;
      return -1;
    }
}