open System 
open System.Text

type Explicit =          
    static member inline ($) (_:int32, _:Explicit) = int
    static member inline ($) (_:int64, _:Explicit) = int64

let inline convert (value:'a): 'b = 
    (Unchecked.defaultof<'b> $ Unchecked.defaultof<Explicit>) value

let inline fromInt (x: int): 'a = convert x

module NumericLiteralG =
    let inline FromZero(): 'a = LanguagePrimitives.GenericZero
    let inline FromOne(): 'a = LanguagePrimitives.GenericOne
    let inline FromInt32 (n: int): 'a = fromInt n

let R() = Console.ReadLine()

let f (x: int64): string =
    let rec g (acc: StringBuilder) x =
        if x = 0L then 
            acc.ToString()
        else 
            let x' = x / 26L
            let y  = int64 'a' + (x - 26L * x') - 1L |> char
            g (acc.Append(y)) x'
    g (StringBuilder()) x 
    |> fun s -> new string(s.ToCharArray() |> Array.rev)

let N = int64 <| R()

f N 
|> printfn "%s"