void minus()
{
    Double_t x[50], y[50];
    Int_t i;
    Double_t rmin[] = {0.0, 1.0, 0.0};
    Double_t rmax[] = {1.0, 0.0, 1.0};

    TCanvas *Hobbes = new TCanvas("Dist","A test",5,5,1400,600);
    Hobbes->cd();
    Hobbes->SetGrid();

    for(i=0;i<50;i++)
    {
	x[i] = (Double_t) i;
    }
    for(i=0;i<50;i++)
    {
	y[i] = -exp(x[i]*0.05);
    }
    TGraph *tg = new TGraph( 50, x, y);
    tg->Draw("ALP");
    printf("%f\n", tg->GetYaxis()->FindBin(y[25]));
}