void cf_simple(const char *fname) {
  TFile *file = new TFile(fname, "READ");
  
  TH1D *num = new TH1D("num", "", 40, 0., 0.4);
  TH1D *den = new TH1D("den", "", 40, 0., 0.4);

  for (int iKt = 0; iKt < 24; iKt++) {
    TH1D *bufNum = (TH1D *)file->Get(Form("hKaonQinvMixKt_1_2_9_Num_bin_%i", iKt));
    TH1D *bufDen = (TH1D *)file->Get(Form("hKaonQinvMixKt_1_2_9_Den_bin_%i", iKt));

    num->Add(bufNum);
    den->Add(bufDen);
  }
  num->Sumw2();
  den->Sumw2();

  float numInt = num->Integral(25, 40);
  float denInt = den->Integral(25, 40);
  float norm = denInt/numInt;
  TH1D *rat = new TH1D("rat", "like sign #pi#pi correlation function (MuDST)", 40, 0., 0.4);
  rat->GetXaxis()->SetTitle("q_{inv} (GeV/c)");
  rat->GetYaxis()->SetTitle("CF(#pi#pi)");
  rat->Divide(num, den, norm);
  TF1 *constFunc = new TF1("constFunc", "1", 0., 0.4);
  rat->Draw();
  constFunc->Draw("SAME");
}