// Reads the points from a txt file and produces a simple comparison graph.
int read_graph_txt_AMPT_data()
{
    auto c=new TCanvas();
    c->SetGridy();
    
    
    TGraphErrors graph1("./data.txt","%lg %lg %lg 0");     // * means not select this column of data
    TGraphErrors graph2("./ALICE.txt","%lg %lg %lg 0");     // * means not select this column of data


   
   
    graph1.SetMarkerStyle(20);
   graph1.SetMarkerColor(kBlue);
    
    graph2.SetMarkerStyle(20);
        graph2.SetMarkerColor(kRed);

    
    // MultiGraph
    // TMultiGraph  *mg  = new TMultiGraph();
    TMultiGraph (mg);
    mg.Add(&graph1);  
    mg.Add(&graph2);
    mg.GetXaxis()->SetTitle("p_{T}(GeV)");
    mg.GetYaxis()->SetTitle("dN/dp_{T}(GeV^{2})");
    //mg.GetYaxis()->SetTitle("#sigma (GeV/c^{2})");
    mg.GetXaxis()->CenterTitle();
    mg.GetYaxis()->CenterTitle();
    //mg.GetYaxis()->SetRangeUser(0.0, 5000);
   
    mg.DrawClone("ALP");

    c->Update();
   // c->GetFrame()->SetBorderSize(12);
    c->Modified();
    //c->SetLogy();
    //c->SetLogx();
   
    //c->BuildLegend();
     return 0;
}