# Missing PiecesWe’re presented with the file “flag.txt” containing 32 lists of numbers. Each list consists of 255 different numbers in range [0, 255] (256 possible values). We can notice that only one value from range [0, 255] is missing from each list, hence the name of the task is “Missing Pieces”. Combining missing values from each list we get the flag.Solution in python:
```# lists from file flag.txtdata = [[...]]
ans = []for v in data:    for i in range(256):        if i not in v:            ans.append(i)
ans = ''.join(map(chr, ans))print(ans) ```
Screenshot with script execution:
![](https://raw.githubusercontent.com/kukuxumushi/HTBxUNI-CTF-final-writeups/master/pictures/2021-03-26-22-39-54.png)