void Der_new()
{

auto h1 = new TH1D("h1_gaus","Mass (amu);Counts",101.0,39.5,140.5);
TH1D*h2 = new TH1D("h2","h2_Derivative", 100.0,40.5,140.5); 

double x;
ifstream inp; 

inp.open("try.txt");
for (int i=0;i<100;i++)
{
  inp>>x;
  h1->SetBinContent(i,x); 
}

TCanvas *c1 = new TCanvas("c1","Without constraint",800,600);


c1->Divide(1,2);
c1->cd(1);
h1->Draw("E1");


Int_t nbins = h1->GetNbinsX();

for(Int_t i=0;i<nbins;i++)
{

double a=h1->GetBinContent(i);
double a_cent=h1->GetBinCenter(i);

double b=h1->GetBinContent(i+1);
double b_cent=h1->GetBinCenter(i+1);

double c=h1->GetBinContent(i+2);
double c_cent=h1->GetBinCenter(i+2);

double e=h1->GetBinContent(i+3);
double e_cent=h1->GetBinCenter(i+3);

double f=h1->GetBinContent(i+4);
double f_cent=h1->GetBinCenter(i+4);



double d = (f-a)/(f_cent-a_cent);
double d_mid = (f_cent+a_cent)/2;

h2->Fill(d_mid,d);

}

c1->cd(2);
gStyle->SetOptStat(1002211);
gStyle->SetOptFit(1111);
h2->Draw("e1");

}