Goal:
    A : Type  l : list A  hd : A  tl : list A
  ============================
   (Some hd = Some hd ∧ tl = tl)


DEBUG:Going to execute:
progress f_equal
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 1: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 2: Backtrace:

Tactic failure:  Cannot find witness.
Level 3: Backtrace:

Tactic failure:  Cannot find witness.
Level 2: Backtrace:

Tactic failure:  Cannot find witness.
Level 1: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 1: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 1: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 1: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.
Level 1: Backtrace:

Tactic failure:  Cannot find witness.
Level 0: Backtrace:

Tactic failure:  Cannot find witness.