<?php
const STR_GROUP = 'ABC';

list($level, $start, $end) = explode(' ', trim(fgets(STDIN)));

$str = STR_GROUP;
if ($level == 1) {
    echo substr($str, $start-1, $end-$start+1).PHP_EOL;
    exit;
}

$str = substr_replace(substr_replace(STR_GROUP, $str, 1, 0), $str, -1, 0);
for ($i=2; $i != $level; $i++) {
    $str = substr_replace(substr_replace(STR_GROUP, $str, 1, 0), $str, -1, 0);
}
echo substr($str, $start-1, $end-$start+1).PHP_EOL;