Definition has_leq_1_elements (A : Ens) :=
  forall (X Y : Ens) (k : IN X A) (l : IN Y A), EQ X Y.Definition has_leq_0_implies_leq_1_Out (l : IN Y A) : EQ X Y := step2.

Theorem has_leq_0_elements_implies_leq_1 : forall (A : Ens) (q : has_leq_0_elements A), has_leq_1_elements A.