solve.py

#!/usr/bin/env python3

from Crypto.Util.number import isPrime
from Crypto.PublicKey import RSA

from gmpy2 import iroot

c = 4881495507745813082308282986718149515999022572229780274224400469722585868147852608187509420010185039618775981404400401792885121498931245511345550975906095728230775307758109150488484338848321930294974674504775451613333664851564381516108124030753196722125755223318280818682830523620259537479611172718588812979116127220273108594966911232629219195957347063537672749158765130948724281974252007489981278474243333628204092770981850816536671234821284093955702677837464584916991535090769911997642606614464990834915992346639919961494157328623213393722370119570740146804362651976343633725091450303521253550650219753876236656017

with open('key') as f:
    key = RSA.import_key(f.read())

n = key.n
e = key.e


def get_next_prime(prime: int) -> int:
    test = prime + 2
    while not isPrime(test):
        test += 2
    return test


while True:
    p, _ = iroot(n, 2)

    while not isPrime(p):
        p -= 2

    q = get_next_prime(p)
    n = p * q
    phi_n = (p - 1) * (q - 1)
    d = pow(e, -1, phi_n)
    p = pow(c, d, n)

    if b'SEE{'.hex() in hex(p):
        print(bytes.fromhex(hex(p)[2:]).decode())
        break