Problem:
Score : 300 points

Problem Statement

1000000000000001 dogs suddenly appeared under the roof of Roger's house, all of which he decided to keep. The dogs had been numbered 1 through 1000000000000001, but he gave them new names, as follows:

the dogs numbered 1,2,\cdots,26 were respectively given the names a, b, ..., z;

the dogs numbered 27,28,29,\cdots,701,702 were respectively given the names aa, ab, ac, ..., zy, zz;

the dogs numbered 703,704,705,\cdots,18277,18278 were respectively given the names aaa, aab, aac, ..., zzy, zzz;

the dogs numbered 18279,18280,18281,\cdots,475253,475254 were respectively given the names aaaa, aaab, aaac, ..., zzzy, zzzz;

the dogs numbered 475255,475256,\cdots were respectively given the names aaaaa, aaaab, ...;

and so on.

To sum it up, the dogs numbered 1, 2, \cdots were respectively given the following names:

a, b, ..., z, aa, ab, ..., az, ba, bb, ..., bz, ..., za, zb, ..., zz, aaa, aab, ..., aaz, aba, abb, ..., abz, ..., zzz, aaaa, ...

Now, Roger asks you:

"What is the name for the dog numbered N?"

Constraints

N is an integer.

1 \leq N \leq 1000000000000001

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer to Roger's question as a string consisting of lowercase English letters.

Sample Input 1

2

Sample Output 1

b

Sample Input 2

27

Sample Output 2

aa

Sample Input 3

123456789

Sample Output 3

jjddja

Solution in PHP (7.4.4) (judge verdict: Accepted)

<?php

fscanf(STDIN, "%d", $n);

$prev;
$i = 1;
$cnt = 0;
while ($n > 0) {
    $i *= 26;
    $prev = $n;
    $n -= $i;
    ++$cnt;
}
/* echo "prev: $prev, cnt: $cnt", PHP_EOL; */

// cnt桁で先頭からprev番目を求める
if ($cnt == 1) {
    echo chr(ord('a') + $prev - 1), PHP_EOL;
    return;
}

$ans = [];
for ($i = 0; $i < $cnt; ++$i) {
    $ans[] = 'a';
}

$i = 0;
--$prev;
while ($prev > 0) {
    $a = $prev % 26;
    /* $ans .= getChar($a); */
    $prev = intdiv($prev, 26);
    --$cnt;
    $ans[$cnt] = chr(ord('a') + $a);
/* echo "しょう: $prev, あまり: $a", PHP_EOL; */
}

echo implode('', $ans), PHP_EOL;

function getChar($n) {
    return chr($n + 96);
}