Goal:
  
  __x2 : Z
  __x1 : Z
  __wit := [] : list ZMicromega.ZArithProof
  __varmap := VarMap.Branch (VarMap.Elt __x2) __x1 VarMap.Empty : VarMap.t Z
  __ff := Tauto.IMPL
            (Tauto.A Tauto.isProp
               {|
                 RingMicromega.Flhs := EnvRing.PEX 1;
                 RingMicromega.Fop := RingMicromega.OpEq;
                 RingMicromega.Frhs :=
                   EnvRing.PEadd (EnvRing.PEopp (EnvRing.PEX 2))
                     (EnvRing.PEc 0)
               |} tt) None
            (Tauto.IMPL
               (Tauto.A Tauto.isProp
                  {|
                    RingMicromega.Flhs := EnvRing.PEopp (EnvRing.PEX 2);
                    RingMicromega.Fop := RingMicromega.OpLe;
                    RingMicromega.Frhs := EnvRing.PEX 1
                  |} tt) None
               (Tauto.A Tauto.isProp
                  {|
                    RingMicromega.Flhs := EnvRing.PEX 1;
                    RingMicromega.Fop := RingMicromega.OpEq;
                    RingMicromega.Frhs := EnvRing.PEopp (EnvRing.PEX 2)
                  |} tt))
       : Tauto.BFormula (RingMicromega.Formula Z) Tauto.isProp
  ============================
   (__x1 = - __x2 + 0 -> - __x2 <= __x1 -> __x1 = - __x2)


DEBUG:Going to execute:
exact
(ZMicromega.ZTautoChecker_sound __ff __wit
   (eq_refl <: ZMicromega.ZTautoChecker __ff __wit = true)
   (VarMap.find 0 __varmap))