#include <iostream>
#include "Pythia8/Pythia.h"
#include "TTree.h"
#include "TFile.h"

using namespace Pythia8;
int main()
{
   int iFile = 1;
   Pythia pythia;
	pythia.readString("Beams:frameType = 4");
	
 	pythia.readString("ProcessLevel:all = off");
	
	pythia.readString("Beams:LHEF=unweighted_events.lhe");
	pythia.init();
// Set up the ROOT TFile and TTree.
  TFile *file = TFile::Open("pytree.root","recreate");
  Event *event = &pythia.event;
  TTree *T = new TTree("T","ev1 Tree");
  T->Branch("event",&event);

for (int iEvent = 0 ; iEvent <= 100 ; iEvent++)
{
if (!pythia.next()){
if (pythia.info.atEndOfFile()){
if (iFile==1)
{
pythia.readString("Beams:LHEF = unweighted_events.lhe");
pythia.init();
++iFile;
continue;
  T->Fill();

 }
else break;
 }
}
}
pythia.stat();
  T->Print();
  T->Write();
  delete file;
return 0;
}