It is 4⁽³⁶⁾ so your calculation is wrong. The last digit of that is 4: https://www.wolframalpha.com/input/?i=%284%5E%283+%5E6%29%29+mod+10

You're doing this instead: (4³)⁶

I see what's wrong in your solution, added some more fixed and random tests to invalidate it. I was confused because the exception you added surely had nothing to do with your code passing by luck.

That's weird because the control function expects "65th" for "6493" (you can test that yourself copying it) and there is not fixed test for that year, are we talking about Python version right?

The expected value for that year is 65, what your code returns is wrong. You can't expect random tests to cover all the years from 1000 to 9999, they're only 100. If by chance it would test for 6493 your code wouldn't pass.

Sorry, but be more specific about what the issue is or it'll get closed.