Add mask (TWCTF) example; 5 reproducible solves total: ps_and_qs, lost_modulus, a2s, russian_threesome, mask

examples/README.md

@@ -10,6 +10,7 @@ patterns from the public `p4-team/ctf` archive.
 | `lost_modulus` | HITCON 2019 Quals | Crypto | RSA leaks `e,d,iqmp,ipmq` but not `n` — recover `n` | `hitcon{1t_is_50_easy_t0_find_th3_modulus_back@@!!@!@!@@!}` |
 | `a2s` | Pwn2Win 2021 | Crypto | 2-round reduced AES — differential attack recovers key | `CTF-BR{bu7_1f_7h0u6h7_c0rrup75_l4n6u463,_l4n6u463_c4n_4l50_c0rrup7_7h0u6h7}` |
 | `russian_threesome` | Hack.lu 2020 | RE/Misc | Inverse-permutation fixed-point on a drum dump (CP1251) | `Кто хочет много знать, тому мало спать.` |
+| `mask` | TokyoWesterns 2020 | Misc | Host bits of `IP/mask` list → base64 → flag | `TWCTF{Are-you-using-a-mask?}` |
 
 ## Run them
 ```bash
@@ -24,4 +25,7 @@ cd examples/a2s && python3 solve.py && cd ../..
 
 # russian_threesome — permutation fixed point
 python3 examples/russian_threesome/solve.py
+
+# mask — IP/mask host bits -> base64
+python3 examples/mask/solve.py
 ```