This challenge is composed by two examples of the use of the Cryptography in Literature.
The first is a classic one. But before decrypting it, look at this visual hint:
And now, the encrypted solution:

Warning: require(GDO6.php): Failed to open stream: No such file or directory in /home/tbs/www/phpgdo/GDO/TBS/chall_include_checker.php on line 15

Fatal error: Uncaught Error: Failed opening required 'GDO6.php' (include_path='.:/usr/share/php') in /home/tbs/www/phpgdo/GDO/TBS/chall_include_checker.php:15 Stack trace: #0 /home/tbs/www/phpgdo/GDO/TBS/challenges/crypto35/index.php(8): require() #1 {main} thrown in /home/tbs/www/phpgdo/GDO/TBS/chall_include_checker.php on line 15