  The integrals defining the two-loop beta-function for the general
renormalizable N=1 supersymmetric Yang--Mills theory, regularized by higher
covariant derivatives, are investigated. It is shown that they are given by
integrals of double total derivatives. These integrals are not equal to zero
due to appearing of delta-functions. These delta-functions allow to reduce the
two-loop integrals to one-loop integrals, which can be easily calculated. The
result agrees with the exact NSVZ beta-function and calculations made by
different methods.
