diff --git a/ISC_421_Controle_4_Saroukhanian_Iliya.py b/ISC_421_Controle_4_Saroukhanian_Iliya.py
index ed058c4884e0d0deb0373233601374f03b8d7d51..fcbc8f15a7b380f49e01efda2631f90d1ab0478d 100644
--- a/ISC_421_Controle_4_Saroukhanian_Iliya.py
+++ b/ISC_421_Controle_4_Saroukhanian_Iliya.py
@@ -232,7 +232,7 @@ def errmax_poly_interpolation(nb_points, interpolation_pts, plot_range):
         for inter_pt in interpolation_pts:
             prod *= pt - inter_pt
 
-        err = (SD.Maximal_derivatives_values[nb_points - 1] /
+        err = (SD.Maximal_derivatives_values[nb_points] /
                math.factorial(nb_points + 1)) * np.abs(prod)
 
         errs_range.append(err)