object Main {
  def main(args: Array[String]): Unit = {
    var num = io.StdIn.readLong

    var count       = 0
    val BASE_NUMBER = 26
    var chars       = ""

    while( num > BASE_NUMBER ) {
      num   -= 1.toLong
      chars += ( num%BASE_NUMBER + 97 ).toChar
      num   /= BASE_NUMBER
    }
    
    chars += ( num + 96 ).toChar
    println( chars )
  }
}