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(* 02110-1301 USA                                                     *)
(********************************************************************** Proof of Huffman algorithm: sTactic.v  Useful tactics  Tactics: Contradict, CaseEq, ElimEq Laurent.Thery@inria.fr (2003) **********************************************************************)

Theorem Contradict1 : forall a b : Prop, b -> (a -> ~ b) -> ~ a.