Scanf.scanf "%d" (fun t ->
    let rec loop i cur =
        if i = t then "T" else
            let x = Scanf.scanf " %d" (fun x -> x) in
            if abs (cur - x) = 1 then loop (i + 1) x
                                 else "F"
    in
    loop 0 0 |> print_endline
)