use strict;
use warnings;

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

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

print join('', @ans);