  Here we are fixing an output of a trivial calculation based on Konsevich's
differential 2-form for the Chern class of polygon bundle. As a result an
interesting combinatorics and arithmetics jumps right out of a jukebox. The
calculation gives very simple rational combinatorial characteristics (we call
it "curvature") of a triangulated $S^1$ bundle over a 2-simplex, which is a
local combinatorial formula for the first Chern class. The curvature is
expressed in terms of cyclic word in 3-character alphabet associated to the
bundle. From the point of view of simplicial combinatorics the word is a
canonical shelling of the total complex. If you know a triangulation of a
bundle - you can really easily compute the Chern class.
