  The inversion formula is given for automorphisms of the Weyl algebras with
polynomial coefficients over a field of characteristic zero. The theorem of
Gabber on the degree of polynomial automorphism is extended. It is proved that
any automorphism of the Weyl algebra with polynomial coefficients is determined
by its left (right) faces (extending the result of J. H. McKay and S. S.-S.
Wang for polynomial automorphisms).
