open System

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

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

    0 
