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

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

match a, b with 
| x, y when x = "H" && y = "H" -> "H"
| x, y when x = "H" && y = "D" -> "D"
| x, y when x = "D" && y = "H" -> "D"
| x, y when x = "D" && y = "D" -> "H"
| _ -> ""
|> printfn "%s"