void get_FRAOrder() {

  gStyle->SetOptStat(0);

  //  TFile*        fHitsFile    = TFile::Open("Gem_3Stations_15GeV_n6000_hitsSELECTOR.root");
  // TFile*        fHitsFile    = TFile::Open("Gem_3Stations_15GeV_n6000_hits_proof.root");
  //    TFile*        fHitsFile    = TFile::Open("Gem_3Stations_15GeV_n6000_tracks_proof.root");
    TFile*        fHitsFile    = TFile::Open("Gem_3Stations_15GeV_n16500_tracks_proof.root");
  TTree*        fHitsTree    = (TTree*) fHitsFile->Get("cbmsim");

  FairEventHeader* fEHeader  = new FairEventHeader();

  fHitsTree->SetBranchAddress("EventHeader.",&fEHeader);

  Int_t nofEvents = fHitsTree->GetEntriesFast();

  TCanvas* eCanv = new TCanvas("entriesOrder","Entries order",10,10,800,600);

  TH1F* entriesOrder = new TH1F("entriesOrder","entries order",nofEvents,-0.5,nofEvents-0.5);

  for ( Int_t iEvent = 0 ; iEvent < nofEvents ; iEvent++ ) {
    fHitsTree->GetEntry(iEvent);
    entriesOrder->Fill(iEvent,fEHeader->GetMCEntryNumber());
  }

  entriesOrder->Draw();

  const Int_t nofWorkers = 4;

  TFile* fWorkerFile[nofWorkers];
  TTree* fWorkerTree[nofWorkers];
  TH1F*  fWorkerEntr[nofWorkers];

  TCanvas* wCanv = new TCanvas("workerDetails","Worker analyzer",10,10,800,600);

  TLegend* aLeg = new TLegend(0.8,0.85,1.0,1.0);

  for ( Int_t iwork = 0 ; iwork < nofWorkers ; iwork++ ) {
    fWorkerFile[iwork] = TFile::Open(Form("worker0.%d_FRA.root",iwork));
    fWorkerTree[iwork] = (TTree*) fWorkerFile[iwork]->Get("cbmsim");
    fWorkerEntr[iwork] = new TH1F(Form("entriesOrder%d",iwork),"worker analyzer",nofEvents,-0.5,nofEvents-0.5);

    fWorkerTree[iwork]->SetBranchAddress("EventHeader.",&fEHeader);
    
    Int_t workerNofEvents = fWorkerTree[iwork]->GetEntriesFast();

    for ( Int_t iEvent = 0 ; iEvent < workerNofEvents ; iEvent++ ) {
      fWorkerTree[iwork]->GetEntry(iEvent);
      fWorkerEntr[iwork]->Fill(fEHeader->GetMCEntryNumber());
    }

    aLeg->AddEntry(fWorkerEntr[iwork],Form("worker 0.%d",iwork),"F");

    fWorkerEntr[iwork]->SetLineColor(2+iwork);
    fWorkerEntr[iwork]->SetFillColor(2+iwork);

    if ( iwork == 0 )
      fWorkerEntr[iwork]->Draw();
    else
      fWorkerEntr[iwork]->Draw("same");

  }
  aLeg->Draw();

}