let findBestT guess n spread =
                if abs(guess) > 1e-6 then
                    let resList = List.init n (fun i -> if i%2=0 then
                                                            NRap (guess-(guess*(float i/float spread))) 0 -infinity
                                                          else
                                                            NRap (guess+(guess*(float i/float spread))) 0 -infinity)

                    let resLL = [NRap guess 0 -infinity]@resList
                    let absMin = match List.filter (fun v -> Option.isSome v && v.Value > -1e-6) resLL with
                                 | [] -> infinity
                                 | l -> abs << List.min <| List.map Option.get l
                    if absMin<infinity then Some(absMin)
                    else None
                else
                    NRap 0. 0 -infinity