let readString() = stdin.ReadLine()
let readStringArray() = stdin.ReadLine().Split(' ');
let readInt() = readString() |> int
let readIntArray() = readStringArray() |> Array.map (fun x -> int x)


let x, a, b = readIntArray() |> fun x -> (x.[0], x.[1], x.[2])

if abs (x - a) < abs (x - b) then "A" else "B" 
|> printfn "%s"