TH1F - read and made histogram

ROOT
8

That’s maybe something for @couet
In the meantime, you could try:

gStyle->SetOptStat(); // just a precaution
((TH1*)(hs->GetStack()->Last()))->Draw("HIST L"); // the sum
hs->Draw("SAME HIST L");

or:

gStyle->SetOptStat(); // just a precaution
TH1 *hl = ((TH1*)(hs->GetStack()->Last())); // the sum
hl->SetNameTitle("MyName", "my title;my X axis;my Y axis");
hl->Draw("HIST L");
hs->Draw("SAME HIST L");

where, instead of:

hl->SetNameTitle("MyName", "my title;my X axis;my Y axis");

you could use:

hl->SetNameTitle(hs->GetName(), hs->GetTitle());
hl->SetXTitle(hs->GetXaxis()->GetTitle());
hl->SetYTitle(hs->GetYaxis()->GetTitle());