hi, I start study about it and I started solving last year’s challenges . l like share my solution with you. Please with comment help me to improve solution and especially my English writing.


```
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Fri Sep 20 11:36:14 2019

@author: matin
"""
import gmpy2
import codecs

ct1=13981765388145083997703333682243956434148306954774120760845671024723583618341148528952063316653588928138430524040717841543528568326674293677228449651281422762216853098529425814740156575513620513245005576508982103360592761380293006244528169193632346512170599896471850340765607466109228426538780591853882736654
ct2=79459949016924442856959059325390894723232586275925931898929445938338123216278271333902062872565058205136627757713051954083968874644581902371182266588247653857616029881453100387797111559677392017415298580136496204898016797180386402171968931958365160589774450964944023720256848731202333789801071962338635072065
e1=13
e2=15
modulus=103109065902334620226101162008793963504256027939117020091876799039690801944735604259018655534860183205031069083254290258577291605287053538752280231959857465853228851714786887294961873006234153079187216285516823832102424110934062954272346111907571393964363630079343598511602013316604641904852018969178919051627


hypothesis_a=pow(ct1,e2,modulus)
hypothesis_b=pow(ct2,e1,modulus)

if hypothesis_a==hypothesis_b :
print("you guess correct Matin :)")

a=gmpy2.invert(13,15)
b=((a*13)-1)/15


xpowernp=pow(ct1,7,modulus)
xpowern=pow(ct2,6,modulus)
xpowern_inverse=gmpy2.invert(xpowern,modulus)
answer_number=(xpowern_inverse*xpowernp)%modulus

answer_hex=hex(answer_number)
answer_finally=codecs.decode(answer_hex[2:] , 'hex')
print("answer is \n")
print(answer_finally,"\n\n :)" )
```

Original writeup (https://atashgahman.ir/write-up-c2-flipping-bits-competition-of-squarectf/).