Goal:
    G : t  z : Z  H : is_true (z <=? 0)
  ============================
   (exists z0 : Z, Some z = Some z0 /\ z0 <= 0)


DEBUG:Going to execute:
t_solver
Level 1: Backtrace:

Tactic failure: congruence failed.
Level 1: Backtrace:

Tactic failure: congruence failed.
Level 1: Backtrace:

Tactic failure: congruence failed.
Level 1: Backtrace:

Tactic failure: congruence failed.
Level 0: Backtrace:

Tactic failure: congruence failed.