That's the most difficult 5 kyu Kata I've solved so far. It can not be done straight forward because of huge k. Need to find optimal algorithm wich is not a trivial task. I would consider it as a 4 kyu Kata.

This Kata is great. It's not too difficult in math way. The hardest part is to adjust it to big numbers.

Approved. Sorry for 2yr delay. Better late than never :/

Don't see any point in using "math/big", as int64 can hadle all test cases for n <= 600.

Can't understand, why will anyone vote as Best Bractice for hardcoded solutions.

Old kata syndrome, can't be changed as of now :-)

Other languages are the same, this kata was not meant to be a performance-based one, but it is over-ranked due to how beta system was established back then

Too late to enforce such changes though...

Nice Kata, but in my opition, its quite easy for 5kyu. It's more like 6 or even 7 kyu.

I got it. Thanks for the explanation! How to remove my ISSUE ? Could not find.

Yes, you're right! Will take it into account in the future :)

First time I was managed to pass all the tests from first attempt. Jahooo!

This test case will lead to 1 Mln different solutions!!! It will be too long to compare the results.

This approach is correct and perfectly fits the time. My solution with the same approach took 2273ms to execute all the tests.

Smart, smart! As usual, akar-O!

Very good! I was close to that solution, sadly I could not make it that beautiful :)