apply H6; rewrite < H7; simplify; apply plus_n_Sm;
|2: intros; rewrite > (eqb_true_to_eq ?? H5); reflexivity
|3: intros; rewrite > sym_plus in H5; rewrite > H5; clear H5 H4 n n1;
cases (m u); cases H4; clear H4; cases H5; clear H5; [assumption]
cases (not_le_Sn_n ? H4)]
clearbody find; cases (find O u);
apply H6; rewrite < H7; simplify; apply plus_n_Sm;
|2: intros; rewrite > (eqb_true_to_eq ?? H5); reflexivity
|3: intros; rewrite > sym_plus in H5; rewrite > H5; clear H5 H4 n n1;
cases (m u); cases H4; clear H4; cases H5; clear H5; [assumption]
cases (not_le_Sn_n ? H4)]
clearbody find; cases (find O u);