object Main extends App {
  val sc = new java.util.Scanner(System.in)
  val n = sc.nextLong()-1
  var m = n

  var d = 26L
  var i = 1
  while (d <= m) {
    m -= d
    d *= 26
    i += 1
  }

  var ans = ""

  while (i > 0) {
    ans = s"${('a' + m % 26).toChar}$ans"
    m /= 26
    i -= 1
  }

  println(ans)
}

