#include<stdio.h>
#include<stdlib.h>
#include <TTree.h>
#include <TFile.h>
#include <TH1F.h>
#include <vector>
int reader()
{



//    TFile *f1 = TFile::Open("output.root");
   
       auto f = new TFile("output.root");
       auto T = (TTree*)f->Get("MONTECARLO");
 


//eventNumber_
  Int_t n_events=(Int_t)T->GetEntries();

  cout<<"number of event : "<<n_events<<endl;

 
for (Int_t i=1;i<=n_events;i++){

cout<<" :  "<<T->GetEntry(i)<<endl;



}
   
 


return (0);
}