Rating:
# extended-fibonacci-sequence-2 (186 solves, 417 points)
## Description
fibs r so much fun here's another one
``nc extended-fibonacci-sequence-2.hsc.tf 1337``
[Extended Fibonacci Sequence 2 ACTUALLY ACTUALLY ACTUALLY NEW.pdf](https://hsctf.storage.googleapis.com/uploads/e1e657e860490efcece6c5cd6efec35c90e4e1882f778675f1ea09274810b2e5/Extended%20Fibonacci%20Sequence%202%20ACTUALLY%20ACTUALLY%20ACTUALLY%20NEW.pdf)
## Solution
This challenge presented no difficulty as I used a practically carbon copy of my [extended-fibonacci-sequence](https://github.com/BASHing-thru-challenges/HSCTF-2021-Writeups/tree/main/algo/extended-fibonacci-sequence) script.
All I did was give ``fib(n)`` new base statements and change ``exFib(n)`` to add instead of concatenate. Once again I used pwntools for nc server interaction.
Final Script:
```python3
from pwn import *
import functools
import re
import time
@functools.lru_cache(None)
def fib(n):
if n == 0:
return 4
elif n == 1:
return 5
return fib(n - 1) + fib(n - 2)
@functools.lru_cache(None)
def exFib2(n):
if n <= 0:
return 0 + fib(n)
return exFib2(n - 1) + fib(n)
def addList(list):
total = 0
for num in list:
total += num
return total
io = process(['nc', 'extended-fibonacci-sequence-2.hsc.tf', '1337'])
io.recvline()
while True:
while True:
try:
data = io.recvline().decode()
print(data)
except EOFError:
print(data)
quit()
match = re.search("(\d{1,})\n", data)
if match is not None:
break
n = int(match.group(0))
print("[RECIEVE]: " + str(n))
summ = []
for i in range(0, n + 1):
summ.append(exFib2(i))
final = str(addList(summ))
final = final[-10:]
io.sendline(final.lstrip('0'))
print("[SEND]: " + final)
```
Run the script... and boom, flag!
## Flag
``flag{i_n33d_a_fl4g._s0m3b0dy_pl3ase_giv3_m3_4_fl4g.}``
