<?php
error_reporting(0);
ini_set("display_errors","Off");
class Jesen {
    public $filename;
    public $content;
    public $me;

    function __wakeup(){
        $this->me = new ctf();
    }
    function __destruct() {
        $this->me->open($this->filename,$this->content);
    }
}

class Ctf {
    function __toString() {
        return "die";
    }
    function open($filename, $content){
        if(!file_get_contents("./sandbox/lock.lock")){
            echo file_get_contents(substr($_POST['b'],0,30).'.');
            die();
        }else{
            file_put_contents("./sandbox/".md5($filename.time()),$content);
            die("or you can guess the final filename?"); 
        }
        
    }
}

if(!isset($_POST['a'])){
    highlight_file(__FILE__);
    die();
}else{
    if(($_POST['b'] != $_POST['a']) && (md5($_POST['b']) === md5($_POST['a']))){
        unserialize($_POST['c']);
    }

}

<?php 
($S = $_GET['S'])?eval("$$S"):highlight_file(__FILE__);