fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)


fun isPossible _ nil = true
  | isPossible old (h::tl) =
    if Int.abs (old - h) = 1 then isPossible h tl
    else false


val () =
    let
        val t = readInt ()
        val x_s = List.tabulate (t, fn _ => readInt ())

        val ans = if isPossible 0 x_s then "T"
                  else "F"
    in
        print (ans ^ "\n")
    end