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

  while (n > 0) {
    val c = if (n % 26 == 0) 25 else (n % 26) - 1
    ans = s"${('a' + c).toChar}$ans"
    if (n == 26) {
      n = 0
    }
    n /= 26
  }

  println(ans)
}
