The differential energy spectrum of cosmic rays in the energy range of 3 × 1014-3 × 1018 eV and the corrected dependence of the mean depth of the maximum «Xmax» of an extensive air shower (EAS) inside the wide energy range of 1015-3 × 1017 eV have been obtained from the data of the Tunka-133 array for 7 years of operation (2009-2017) and the TAIGA-HiSCORE array for the 2019-2020 season of operation. At the extremely high energy, our results agree with the results of the Pierre Auger Observatory based on direct measurements of the maximum depth by the observation of fluorescent light from EAS. The recalculation from the «Xmax» to the parameter $\left\langle {\ln A} \right\rangle $, which characterizes the average composition of the primary cosmic rays, is presented....