#a #b #c #H @le_plus_to_minus_r //
qed.
+lemma lt_plus_Sn_r: ∀a,x,n. a < a + x + (S n).
+/2 width=1/ qed.
+
theorem lt_S_S_to_lt: ∀n,m:nat. S n < S m → n < m.
(* demo *)
/2/ qed-.
lemma to_max: ∀i,n,m. n ≤ i → m ≤ i → max n m ≤ i.
#i #n #m #leni #lemi normalize (cases (leb n m))
normalize // qed.
-