Code resolving chall ^3^
```
from PIL import Image

folder_broken = "./QuickFix/"

total_frame = 100

png_header = "89504e470d0a1a0a0000000d"
jpg_header = "ffd8ffe000104a4649460000000d"

def fix_magic_bytes():
# image size 20x20 -> flag image after concat with size 20 * 100 x 20 *100
flag = Image.new('RGB',(2000,2000))

for first in range(total_frame):
for second in range(total_frame):
fp_read = open("{}flag_{}_{}.jpg".format(folder_broken,first,second),"rb")
hex_file_broken = (fp_read.read()).encode("hex")

hex_file_fixed = hex_file_broken.replace(jpg_header,png_header)

fp_write = open("temp.png","wb")
fp_write.write(hex_file_fixed.decode("hex"))
fp_write.close()

img_open = Image.open("temp.png")
flag.paste(img_open,(first*20,second*20))

fp_read.close()

flag.save("flag.png")
print "[+] Open flag.png to get flag"

if __name__ == '__main__':
fix_magic_bytes()
```

Original writeup (https://github.com/dianguc38/CTF/blob/master/DarkCTF2020/solve.py).