int fitHisto()
{
  TFile* file = new TFile("file.root","UPDATE");
  TDirectoryFile* dir = (TDirectoryFile*)file->Get("dir");
  TH1F* h = (TH1F*)dir->Get("h");
  
  h->Fit("gaus","Q0");
  
  file->Write();
  file->Close();

  return 0;
}