// Convert roman to decimal
   cstart2 = high_resolution_clock::now();
   for ( auto const& r : roman_list ) {
      // std::cout << roman_to_dec(r) << '\n';
      fast_io::io::println(roman_to_dec(r));
   }
   cend2 = high_resolution_clock::now();
   double ctaken2 = elaspe_time(cend2, cstart2);
   std::cerr << "roman_to_dec time : " << std::setw(8) << ctaken2 << " secs\n";
   
   double ctaken = elaspe_time(cend2, cstart1);
   std::cerr << "total time        : " << std::setw(8) << ctaken   << " secs\n";