triplesOfLatinLetters

<?php
/**
 * Created by PhpStorm.
 * User: Toshiba
 * Date: 4.10.2018 г.
 * Time: 18:17
 */

$n = intval(readline());

for ($i = 0; $i < $n; $i++) {

    for ($j = 0; $j < $n; $j++) {

        for ($k = 0; $k < $n; $k++) {
            echo chr(97 + $i) . chr(97 + $j) . chr(97 + $k) . PHP_EOL;
        }
    }
}