#include <sstream>
#include <iostream>
#include <iterator>
#include <set>
#include <algorithm>
void dothis()
{
   std::istringstream afile ("1 2 10\n\n 15\n 2 5 ");
   std::istream_iterator<int> abeg(afile), aend;
   std::set<int> aset(abeg, aend);

   std::istringstream gfile ("10 11 100 -1 0\n1 2 5\n");
   std::istream_iterator<int> gbeg(gfile), gend;
   std::set<int> gset(gbeg, gend);

// no files on ideone, using strings and cout
//   std::ofstream cfile("c.txt");
   set_symmetric_difference(aset.begin(), aset.end(),
                            gset.begin(), gset.end(),
                            std::ostream_iterator<int>(std::cout, "\n"));
}
int main()
{
    dothis();
}