Goal:
  
  G : t
  HI : invariants
  n : Z
  x : V.t
  y : V.t
  z : Z
  xy : lsp x y = Some z
  H : n <= z
  ============================
   (exists k : Z, Some z = Some k /\ n <= k)


DEBUG:Going to execute:
eexists; split
DEBUG LTAC Evaluated term: lsp