{
  // gStyle->SetOptFit();
  Int_t n = 160;
  Double_t xl = 380., xr = xl + n; // make sure "bin width" = 1.
  TH1D *h = new TH1D("h", "h;Channel;Counts", n, xl, xr);
  TF1 *f = new TF1("f", "gausn(0) + gausn(3) + pol2(6)", xl, xr);
  TF1 *pol2  = new TF1("Mypol2","pol2", xl, xr);
  TF1 *g1    = new TF1("Myg1","gausn", xl, xr);
  TF1 *g2    = new TF1("Myg2","gausn", xl, xr);
  //"gausn” Normalized form of the gaussian function with 3 parameters f(x) = p0*exp(-0.5*((x-p1)/p2)^2)/(p2 *sqrt(2PI))  

  f->SetParNames("Area_1", "Mean_1", "Sigma_1", // gausn(0)
                 "Area_2", "Mean_2", "Sigma_2", // gausn(3)
                 "c", "b", "a"); // pol2(6)
  // f->Print();
  f->SetParameters(5.e4, 430., 10., // gausn(0)
                   4.e4, 490., 10., // gausn(3)
                   400., 0.4, -0.002); // pol2(6)
  // gRandom->SetSeed(0);22// make it "really random"

  h->FillRandom("f", Int_t(f->Integral(xl, xr) + 0.5)); //+0.5 is Just to get the “nearest” integer.


  h->Fit(f, "L"); // e.g., "" or "L"
  f->Delete();

  g1->SetParameters(5.e4, 430., 10.);
  g2->SetParameters(4.e4, 490., 10.);
  pol2->SetParameters( 400., 0.4, -0.002);

  g1->SetLineColor(kBlue);
  g2->SetLineColor(kBlue);

  g1->Draw("same");
  g2->Draw("same");

  pol2->SetLineColor(kBlack);
  pol2->Draw("same");

}