public function viewHint(Paper $paper, Hint $hint)
    {
        $log = $this->om->getRepository('UJMExoBundle:LinkHintPaper')
            ->findOneBy(['paper' => $paper, 'hint' => $hint]);

        if (!$log) {
            $log = new LinkHintPaper($hint, $paper);
            $this->om->persist($log);
            $this->om->flush();
        }

        return $hint->getValue();
    }