import java.util.*

fun main(args: Array<String>) {
  val sc = Scanner(System.`in`)
  val n = sc.nextLong()

  // val nmax = 1_000_000_000_000_001

  var total = 0L
  var tmp = 26L
  var digit = 0
  while (total < n) {
    digit++
    total += tmp
    tmp *= 26L
  }

  val pre = total - (tmp / 26L)
  val now = n - pre

  var a = now - 1L
  val ans = mutableListOf<Char>()
  for (i in digit - 1 downTo 0) {
    val tmp2 = Math.pow(26.0, i.toDouble()).toLong()
    val tmp3 = a / tmp2

    val c = (tmp3 + 'a'.toInt()).toChar()
    ans.add(c)

    a %= tmp2
  }

  println(ans.joinToString(""))

}


