open System

let rec f (n : int64) :string  =
    if n = 0L then ""
    else
        let nm = n - 1L
        let nm26 = nm / 26L
        (f nm26) +   string(char(int64('a')+ nm%26L))

[<EntryPoint>]
let main argv =
    let [|n|] = stdin.ReadLine().Split() |> Array.map int64
    f n |> printf "%s"

    0 
