Insert 3 histograms in 1 Canvas

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5

I read this topic : “Merge more than one canvas in one”

and i modified my code:

{	
	TCanvas *C = new TCanvas("C", "Main Canvas", 960, 1100);

    C->Divide(1,3);

	TCanvas *c1 = new TCanvas ("c1", "Distribuzione random gaus", 700, 500);
	TCanvas *c2 = new TCanvas ("c2", "Distribuzione random lineare", 700, 500);
	TCanvas *c3 = new TCanvas ("c3", "Distribuzione random landau", 700, 500);

	TFile *f= new TFile ("esercizio_esame.root", "recreate");

	

	TH1D *h_1 = new TH1D ("Istogramma Gauss", "Distribuzione random Gaus", 100, -20, -20);

	gRandom = new TRandom1();

	for(Int_t i=0; i<10000; i++){

		h_1->Fill(gRandom->Gaus(5,3));

	}

	TF1 *g = h_1->GetFunction("gaus");

	h_1->Fit("gaus");

	c1->cd();

	h_1->DrawCopy();

	h_1->Write();

	C->cd(1);
    c1->DrawClonePad();

	TH1D *h_2 = new TH1D ("Istogramma Lineare", "Distribuzione random Lineare", 200, 0, 200);

	gRandom = new TRandom2();

	for(Int_t i=0; i<100000; i++){

		h_2->Fill(gRandom->Integer(200));

	}

	c2->cd();

	h_2->DrawCopy();

	h_2->Write();

	C->cd(2);
    c2->DrawClonePad();

	TH1D *h_3 = new TH1D ("Istogramma Landau", "Distribuzione random Lineare", 50, 0, 80);

	gRandom = new TRandom3();

	for(Int_t i=0; i<100000; i++){

		h_3->Fill(gRandom->Landau(2));

	}

	c3->cd();

	h_3->DrawCopy();

	h_3->Write();

    C->cd(3);
    c3->DrawClonePad();


	f->Close();

}

Now I see 4, the 3 canvas that i created before (How can I un-draw them?) and the main canvas, but it was empty…