void test()
{
  const Int_t nfile = 1;  
  const Int_t ncentrality = 1; 
  TH2D *h2S[nfile];
  TH2D *h2B[nfile];
  
  Double_t PI=TMath::Pi();
 
  for(int k=0; k<nfile; k++){
    h2B[k] = new TH2D(Form("h2B_%d",k), Form("h2B_%d", k), 100,-1.6,1.6,200,-1.5,2.*PI-1.5);
  }
  
  TFile *fin[nfile];
  TH2D *htmp;
  char finName[128]; 
  char histName[128];
  for(int ic=0; ic<nfile; ic++){
    fin[ic] = new TFile("./file.root","READ");
    
    for(int ih=0; ih<ncentrality; ih++){
      htmp = (TH2D*) fin[ic]->Get(Form("Sh2_Deta_Dphi_%d",ih));
      h2S[ic]->Add(htmp);
    
      htmp = (TH2D*) fin[ic]->Get(Form("Bh2_Deta_Dphi_%d",ih));
      h2B[ic]->Add(htmp);
     }
   }
}