∀ {α : Type u_1} [inst : BEq α] [inst_1 : LawfulBEq α] {xs : List α} {xc : (x : α) × Fin (List.count x xs)}
  (h :
    List.countBefore xs[↑(xs.sigmaCountToIdx xc)] xs ↑(xs.sigmaCountToIdx xc) + 1 ≤
      (List.filter (fun x => x == (xs.idxToSigmaCount (xs.sigmaCountToIdx xc)).fst) xs).length),
  (List.findIdxs (fun x => x == (xs.idxToSigmaCount (xs.sigmaCountToIdx xc)).fst)
        xs)[List.countBefore xs[↑(xs.sigmaCountToIdx xc)] xs ↑(xs.sigmaCountToIdx xc)] <
    xs.length