<?php

	ini_set('memory_limit', '-1');
	function generate_str($a = "0123456789", $l = 1) {
	    $base = "0123456789abcdefghijklmnopqrstuvwxyz";
	    $b = strlen($a);
	    $count = pow($b, $l);
	    for ($i=0;$i<$count;$i++) {
	    	echo strtr(str_pad(base_convert($i, 10, $b), $l, "0", STR_PAD_LEFT), $base, $a),"\r\n";
	  	}
    }
    for ($i=5; $i <= 20; $i++) {
    	generate_str("0123456789abcdefghijklmnopqrstuvwxyz", $i);
    }