use strict;
use warnings;

my $n = <>;
my @abc = ('A'..'Z');
my @ans = ();

if($n == 0){
  unshift @ans, $abc[$n];
}else{
  while($n > 0){
    if(!@ans){
      unshift @ans, $abc[$n % 26];
    }else{
      unshift @ans, $abc[($n % 26)-1];
    }
    $n = int($n/26);
  }
}
print join('', @ans);