  Let $H_n$ be the minimal number such that any $n$-dimensional convex body can
be covered by $H_n$ translates of interior of that body. Similarly $H_n^s$ is
the corresponding quantity for symmetric bodies. It is possible to define $H_n$
and $H_n^s$ in terms of illumination of the boundary of the body using external
light sources, and the famous Hadwiger's covering conjecture (illumination
conjecture) states that $H_n=H_{n}^s=2^n$.
  In this note we obtain new upper bounds on $H_n$ and $H_{n}^s$ for small
dimensions $n$. Our main idea is to cover the body by translates of John's
ellipsoid (the inscribed ellipsoid of the largest volume). Using specific
lattice coverings, estimates of quermassintegrals for convex bodies in John's
position, and calculations of mean widths of regular simplexes, we prove the
following new upper bounds on $H_n$ and $H_n^s$: $H_5\le 933$, $H_6\le 6137$,
$H_7\le 41377$, $H_8\le 284096$, $H_4^s\le 72$, $H_5^s\le 305$, and $H_6^s\le
1292$.
  For larger $n$, we describe how the general asymptotic bounds $H_n\le
\binom{2n}{n}n(\ln n+\ln\ln n+5)$ and $H_n^s\le 2^n n(\ln n+\ln\ln n+5)$ due to
Rogers and Shephard can be improved for specific values of $n$.
