import java.util.Scanner

object Main extends App {

  def readALine(c:Int, ac:List[Int]=Nil):List[Int] =
    if (c > 0) readALine(c-1, sc.nextInt::ac) else ac.reverse
  // def readLines(r:Int, c:Int, ac:List[List[Int]]):List[List[Int]] =
  //   if (r > 0) readLines(r-1, c, readALine(c, Nil)::ac) else ac.reverse
  val sc = new Scanner(System.in)
  val N = sc.nextLong

  val divisor = 26

  def solver(n:Long, al:List[Int]):List[Int] = {
    // println(s"debug n:$n al:$al")
    if (n / divisor ==0)
      (n % divisor).toInt::al
    else
      solver((n-divisor)/divisor, ((n-divisor) % divisor).toInt::al)
  }

  println(solver(N-1, Nil).map((x)=>(x+97).toChar).mkString(""))

}