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


fun quicksort [] = []
  | quicksort (h::tl) =
    let 
        val (s, b) =
            List.foldl
                (fn (x, (small, big)) =>
                    if x <= h then (x::small, big)
                    else (small, x::big))
                ([], [])
                tl
    in
        (quicksort s) @ [h] @ (quicksort b)
    end


val () =
    let
        val ha = readInt ()
        val hb = readInt ()
        val hc = readInt ()

        val sorted = List.rev (quicksort [ha, hb, hc])

        fun findAns [] = ""
          | findAns (h :: tl) = if h = ha then "A\n" ^ findAns tl
                                else if h = hb then "B\n" ^ findAns tl
                                else "C\n" ^ findAns tl
    in
        print (findAns sorted)
    end