import math._
import scala.collection.mutable.ArrayBuffer;

object Main {
  def main(args: Array[String]) {
    val sc = new java.util.Scanner(System.in)
    var n = sc.nextLong + 1

    val cs = new ArrayBuffer[Char]
    while (n > 0) {
      val m = (n - 1) % 26
      cs.append((m + 'A').toChar)
      n = (n - 1) / 26
    }
    println(cs.mkString.reverse)
  }
}