<?php
  $n = intval(trim(fgets(STDIN)));
  $i;
  $work=26;
  $ans='';
  $array = array();

  for($i=0;$i<$n && ($n > $work);$i++){
    $work = $work*27;
  }
  if($n==$work) $ans = $ans . chr(65);
  for(;$i>=0;$i--){
    $array+=array($work=>floor($n/$work));
    $n -= $work*floor($n/$work);
    $work = $work/27;

    if($n > 0) {
      $ans = $ans . chr(65+floor($n/$work));
    }
    else
      $ans = $ans . chr(65);

  }
  printf("$ans\n");