  A new method based on the R'-operation of the renormalization theory is
proposed for the numerical calculation of the renormalization constants in the
theory of critical behaviour. The problem of finding residues of the poles of
the Green's functions at \epsilon = 0, where \epsilon = 4 - d, is reduced to
the evaluation of multiple UV-finite integrals, which can be performed by means
of standard integration programs. The method is used to calculate the
renormalization group functions of the model A of critical dynamics in
four-loop approximation. Dynamical exponent z of the model A is calculated in
the fourth order of the \epsilon-expansion.
