fact: Definition quotient X (R : X -> X -> Prop) Y := { cls : X -> Y & { rpr : Y -> X | (forall y, cls (rpr y) = y) /\ (forall x1 x2, R x1 x2 <-> cls x1 = cls x2) } }.
imports: List Arith Lia Permutation Relations Bool Eqdep_dec Undecidability.Shared.Libs.DLW.Utils(utils_tac utils_nat)