<?php
  $n = intval(trim(fgets(STDIN)));
  $i;
  $work=26;
  $ans='';
  $array = array();
  for($i=0;$i<$n && ($n > $work);$i++){
    $work = $work*27;
  }
  for(;$i>=0&&$work>26;$i--){
    $array+=array($work=>floor($n/$work));
    $n -= $work*floor($n/$work);
    $work = $work/27;


    if(floor($n/$work) > 0)$ans = $ans . chr(64+floor($n/$work));
    else $ans = $ans . chr(65);
  }
  //これは教育やろなあ・・・
  if($n==26) $ans = $ans . chr(65);
  $ans = $ans . chr(65+$n%26);
  printf("$ans\n");