{
gROOT->Clear();
gROOT->Reset();

//Load chain.
TFile *Achain = new TFile("/disk/usr4/ethrane/upmu3ET/tanaka/tanaka.root");

//Create histograms.
TH1F *Hohit8mThru = new TH1F("Hohit8mThru","ohit8m (exit)",60,0,60);
TH1F *Hohit8mStop = new TH1F("Hohit8mStop","ohit8m (exit)",60,0,60);

//Fill histogram with ehit8m.  (The default tree is h1.)
h1->Draw("Um_ohit8m>>Hohit8mThru","Pid_flg==1");
h1->Draw("Um_ohit8m>>Hohit8mStop","Pid_flg==2","same");

//Color each histogram.
Hohit8mStop->SetFillColor(2);
Hohit8mThru->SetFillColor(3);
Hohit8mStop->SetFillStyle(3013);

//Stack histograms.
THStack hs("hs","stack");
hs.Add(Hohit8mThru);
hs.Add(Hohit8mStop);

//remove old .root file with command line prompt
.! rm pid.root

//Save stack.
TFile f("pid.root","new");
hs.Write();   

//Save as gif.
c1->Print("pid.gif");

}