void hist() {


   TFile *f = new TFile("1.root","RECREATE");
   TH1D *h1 = new TH1D("h1","x and Y distribution",10000,0,2500);
   TTree *T = new TTree("ntuple","data from dat file");
   Long64_t nlines = T->ReadFile(Form("13MeV-Ge-19-03-2020.dat"),"x/D:y/D");
   T->Project("h1","x","y");
   printf(" found %lld points\n",nlines);
   T->Draw("x","y");
   T->Write();

}