let ALPHA = ['A'..'Z']

let doIt () =
    let rec odai rlist N =
        let Q, R = N / 26UL, ALPHA.[int (N % 26UL)]

        if Q = 0UL then R :: rlist
        else odai (R :: rlist) (Q - 1UL)

    let N = stdin.ReadLine () |> uint64
    odai [] N |> Array.ofList |> (fun arr -> System.String(arr)) |> printfn "%s"

doIt ()