Section Arg3_1.
Definition monotone3 T0 T1 T2 (gf: rel3 T0 T1 T2 -> rel3 T0 T1 T2) :=
forall x0 x1 x2 r r' (IN: gf r x0 x1 x2) (LE: r <3= r'), gf r' x0 x1 x2.
Variable T0 : Type.
Variable T1 : forall (x0: @T0), Type.
Variable T2 : forall (x0: @T0) (x1: @T1 x0), Type.
Variable gf : rel3 T0 T1 T2 -> rel3 T0 T1 T2.
Arguments gf : clear implicits.

Theorem paco3_2_1_acc: forall
l r_0 r_1 (OBG: forall rr (INC: r_1 <3= rr) (CIH: l <_paco_3= rr), l <_paco_3= paco3_2_1 gf_0 gf_1 r_0 rr),
l <3= paco3_2_1 gf_0 gf_1 r_0 r_1.