  It is suggested to determine the $A$ dependence of distortions of the nucleon
structure function $F_2(x)$ by summing the distortions over an interval ($x_1,
x_2$). It was found from the analysis of data on deep--inelastic scattering of
muons and electrons from nuclei that the $A$ dependence of distortion
magnitudes obtained in each of three regions under study, namely shadowing,
antishadowing and the EMC effect region, follow the same functional form, being
different in the normalizing factor only. All the available data give evidence
for the saturation of the distortion magnitude with rising $A$.
