import java.util.Scanner

import scala.io.StdIn._
object Main extends App {


  val n = scala.io.StdIn.readLine().toLong

  def solve(): String = {
    f(n)
  }

  def f(num: Long): String = {
    if(num == 0) ""
    else {
      val num0Index = num-1
      f(num0Index / 26) + ((num0Index % 26) + 'a').toChar
    }
  }

  println(solve())

}
