Goal:
  
  m : t
  a : t
  l : list t
  IHl : forall n : t, fold_left max l n = m -> n = m \/ In m l
  n : t
  H : In m l
  ============================
   (In m l)


DEBUG:Going to execute:
solve
[ trivial
with eq_true
| reflexivity
| symmetry; trivial
| contradiction
| congruence ]