(* Ugly tacty to resolve sign condition for N *)
Require Export NGroundTac.
Open Scope N_scope.

Theorem Nmult_lt_compat_l: forall n m p, n < m -> 0 < p -> p * n < p * m.
intros n m p H1 H2; apply Nlt_lt; repeat rewrite N2Nat.inj_mul.