fact: Definition find_pair : forall A:eqType, forall P:A->bool, forall Q:A->A->Prop, forall l:seq A, forall a b:A, P a -> ~P b -> (forall l1 l2 x y, a::l ++ b::nil= l1 ++ x :: y :: l2 -> Q x y) -> {c :A & { d | Q c d /\ P c /\ ~P d}}.
imports: ZArith Zwf Lia mathcomp(ssreflect eqtype ssrbool ssrnat div fintype seq ssrfun order) mathcomp(bigop fingroup choice ssralg ssrnum rat poly) pol