  This paper presents the results of calculation of element overproduction in
the S-Cl region during helium and carbon burning in massive stars (25 Ms).
Calculations for a given set of differential equations were performed using
integrated mathematical systems. The authors think that this method may be
successfully adopted for other physical problems in which solving
nuclear-reaction network play an important role, in particular for the problem
of transmutation of heavy elements and chemical kinetics.
