Goal:
  
  n : Z
  a : Z
  l : list Z
  IHl : forall m : Z, n <= m \/ Exists (Z.le n) l -> n <= fold_left Z.max l m
  m : Z
  H0 : n <= a
  z1 : Z
  H1 : m < a /\ z1 = a \/ a <= m /\ z1 = m
  ============================
   (n <= z1)


DEBUG:Going to execute:
xlia zchecker