  We determined the \fodd\ values, $0.46\pm0.08$, $0.51\pm0.09$, $0.50\pm0.13$,
$0.48\pm0.12$, which correspond to the r-contribution 100\% for four r-II
stars, \cs, \hen, \hes\, and \het, respectively. Our results suggest that
almost all of the heavy elements (in the range from Ba to Pb) in r-II stars
have a common origin, that is, from a single r-process (the main r-process). We
found that the \fodd\ has a intrinsic nature, and should keep constant value of
about 0.46 in the main r-process yields, which is responsible for the heavy
element enhancement of r-II stars and of our Galaxy chemical enhancement. In
addition, except the abundance ratio [Ba/Eu] the \fodd\ is also an important
indicator, which can be used to study the relative contributions of the r- and
s-process during the chemical evolution history of the Milky Way and the
enhancement mechanism in stars with peculiar abundance of heavy elements.
