let f i c =
    let cn= (int c)-(i+1)%26
    if cn<65 then (cn+26) |> char |> string
    elif cn>90 then (cn-26) |> char |> string
    else cn |> char |> string
stdin.ReadLine()
|> Seq.mapi f
|> Seq.reduce (+)
|> stdout.WriteLine