  Generic classical electron motion in a strong perpendicular magnetic field
and random potential reduces to the bond percolation on a square lattice. Here
we point out that for certain smooth 2D potentials with 120 degrees rotational
symmetry this problem reduces to the site percolation on a triangular lattice.
We use this observation to develop an approximate analytical description of the
integer quantum Hall transition. For this purpose we devise a quantum
generalization of the real-space renormalization group (RG) treatment of the
site percolation on the triangular lattice. In quantum case, the RG
transformation describes the evolution of the distribution of the $3\times 3$
scattering matrix at the sites. We find the fixed point of this distribution
and use it to determine the critical exponent, $\nu$, for which we find the
value $\nu \approx 2.3-2.76$. The RG step involves only a single Hikami box,
and thus can serve as a minimal RG description of the quantum Hall transition.
