Rating: 4.0

The problem is:

exploit = input('? ')
if eval(b64encode(exploit.encode('UTF-8'))) == math.pi:

Note that the submitted string will be encoded into UTF-8 and then encoded into Base64.

With Base64 characters, we can write some numbers and operators `0123456789+/`
(and hex `abcdefABCDEFx`, but wasn't used in my solution).

My teammate azon found that these 4-character unit can be passed the above criteria
(written in Base64 characters, can be encoded into UTF-8):

- `[0-3][4-7][014589][0-9+/]`
- `[4-7][4-7][26+][0-9+/]`

With this units, we can write `'340/340+340/340+340/340+776/140/140+340/3400'` and this value is `3.1395918367346938`, for example.

Then we wrote a searching program and got flag.

Original writeup (https://gist.github.com/n-ari/3fcabfa817a74cd91ca718f357929a04).