high (too low) for longer (shorter) tracking times and as such they are not suitable for discrimination between the different nuclei. (We note that we use only one value of tracking time for whole energy range of particles.)

The propagation of particle was stopped in a moment when the particle escaped from the Galaxy. The escape occurred when the particle crossed the Galaxy geometrical boundary. Otherwise, if the particle stayed within the Galaxy for time longer than $T=3\times10^{12}$, simulation was also stopped and the particle was simply taken as not escaped. From these values of the particle escape rates one can easily calculate the chemical composition of CRs.

Our starting chemical composition is taken from [@wiebel], who summarized results of several experiments for energy $10^{12}$ eV. We have divided all nuclei into five groups according to their mass. From each group we choose a nucleus that is the best representative. In this way we have chosen protons and nuclei of helium, oxygen, magnesium and iron as group representatives, with initial abundance equal to $42\%$, $26\%$, $13\%$, $9\%$ and $10\%$, respectively. As the indicator of the composition, we use mean value of the logarithm of mass number $A$, $$<\ln (A)>=\frac{\sum n_i 