Find the minimal polynomial $m(x)$ of $\left[\begin{array}{ccccc} -6 &1 &0 &0 &0\cr 0 &-6 &0 &0 &0\cr 0 &0 &-6 &0 &0\cr 0 &0 &0 &1 &0\cr 0 &0 &0 &0 &1 \end{array}\right]$.
$m(x) =$