//Draw circle with holes
TCanvas *circle_with_holes(){
  TCanvas *c1 = new TCanvas("c1", "c1", 500, 500);
  c1->Range(0, 0, 1, 1);
  gPad->SetFillColor(kGreen); //background color

  TEllipse *circle = new TEllipse(0.5, 0.5, 0.4);
  circle->SetLineWidth(6);
  circle->SetFillStyle(1001); //solid
  circle->SetFillColor(kGray);
  circle->Draw("Lf");

  TEllipse *hole1 = new TEllipse(0.4, 0.4, 0.1);
  hole1->SetLineWidth(6);
  hole1->SetFillStyle(0); //hollow
  hole1->Draw("L");

  TEllipse *hole2 = new TEllipse(0.6, 0.6, 0.1);
  hole2->SetLineWidth(6);
  hole2->SetFillStyle(0); //hollow
  hole2->Draw("L");

  return c1;
}