void sim(Int_t nev=4) {
  AliSimulation simulator;
  simulator.SetMakeSDigits("TRD TOF PHOS HMPID EMCAL MUON FMD ZDC PMD T0 VZERO");
  simulator.SetMakeDigitsFromHits("ITS TPC");
  simulator.SetWriteRawData("ALL","raw.root",kTRUE);

  TStopwatch timer;
  timer.Start();
  simulator.Run(nev);
  timer.Stop();
  timer.Print();
}