double fitf(Double_t *x,Double_t *par){

double fitval=(par[0]*x[0]+par[1]*x[1]+par[2]);
        return fitval;
}


void rr()
{
	const int bin=40;
TH3F *h=new TH3F("h","h",bin,0,50,bin,0,50,bin,0,50);
TRandom ran;
double nn=22;
for(int i=0;i<5000;i++){h->Fill(ran.Poisson(nn),ran.Poisson(nn),ran.Poisson(10));
}
double N=h->GetBin(bin,bin,bin);
cout<<N<<endl;;
TF2  *f1 = new TF2("f1",fitf,0,50,0,50,3);
f1->SetParameters(-2,-1,1);
h->Fit(f1);
f1->Draw("surf");
h->Draw("same BOX2 ");

}