feat: implement calculate function

[kolbryt]

No description provided.

[ziobron]

@kolbryt, we do not have your data in the Coders School database.

1. Please fill in this form https://forms.gle/rkzLsMUSBdnGQgdM9
2. Edit this PR to run this automation once again (you can just add a space in the description or title).
3. Wait one minute. If any label was added to this PR (like Standard, Premium, Podstawy C++, STL) then everything is fine :)
4. If your solution passed, but nothing happens, modify your code (eg. add an empty line) to run the workflow again.

If you don't know what to do - ask on Discord and provide a link to this PR.

[ziobron]

✅ CI Passed - Task: formatting_check
New user detected (@kolbryt). Trying to automatically map accounts.

[ziobron]

✅ CI Passed - Task: formatting_check
🏅 Granted 1 XP for @kolbryt

[ziobron]

✅ CI Passed - Task: calculate
🏅 Granted 6 XP for @kolbryt

[ziobron]

✅ CI Passed - Task: formatting_check
🏅 Granted 1 XP for @kolbryt