{
   auto c2 = new TCanvas("c2","c2",600,400);
   auto hsurf = new TH2F("hsurf","Option SURF example ",30,-4,4,30,-20,20);
   float px, py;
   for (Int_t i = 0; i < 25000; i++) {
      gRandom->Rannor(px,py);
      hsurf->Fill(px-1,5*py);
      hsurf->Fill(2+0.5*px,2*py-10.,0.1);
   }
   hsurf->Draw("SURF");
}