void cl()
{
	auto c = new TCanvas("cc", "cc", 800, 300);
	int keep[7]= {1,2,3,9,21,41};
	const int NMbins = 5;
	double Mbins[6]={0.,25.,50.,200., 500.,1000.};
	auto h1 = new TH1F("h1", "h1", NMbins, Mbins);
	Int_t nfill = 5000;
	while (nfill -- > 0) {
		h1->Fill(200*gRandom->Gaus() + 400); 
	}
	h1->SetNdivisions(-40);
	h1->Draw();
	c->Update();
	TAxis *ax = h1->GetXaxis();
	// remove unwanted labels
	for (int il=1; il<=40; il++) {
		Bool_t remove = kTRUE;
		for (int k=0; k<7; k++){
			if (il == keep[k]) {
				remove = kFALSE;
				break;
			}
		}
		if (remove) {
			ax->ChangeLabel(il, -1, -1, -1, -1, -1, " ");
		}
	}
	c->Modified();
	c->Update();
}