void na49geomfile()
{
   gBenchmark->Start("geometry");
   TGeometry *n49 = (TGeometry *)gROOT->FindObject("na49");
   if (n49) {
      TFile na("na49.root", "RECREATE");
      n49->Write();
      na.Write();
   }
   gBenchmark->Show("geometry");
}