import java.util.Scanner

object Main extends App {
  val sc = new Scanner(System.in)
  val N = sc.nextInt

  val z = {
    val buf = new StringBuilder
    @scala.annotation.tailrec
    def loop(n: Int): Unit = {
      buf.append(((n - 1) % 26 + 'a').toChar)
      if (n != 0) loop((n - 1) / 26)
    }
    loop(N)

    buf.reverse.toString.tail
  }
  println(z)
}
