object Main extends App {
  val sc = new java.util.Scanner(System.in)
  val n = sc.nextLong()

  def solve(n: Long): String = {
    if (n == 0) {
      ""
    } else {
      s"${solve((n - 1) / 26)}${('a' + ((n - 1) % 26)).toChar}"
    }
  }

  println(solve(n))
}
