please do not raise an issue to ask for help. your latest code submission does not time out, but it is incorrect

Strange, my solution works in online C compilers, but here it goes to overclocking 12000ms.

Your solution cannot be correct for large numbers. The Convert.ToInt64(Math.Pow(n, 2)) does not seem to be a correct thing to do.

LC translation

The recursive version worked locally but not here

I used C#.

In what language?
What is your code?

Anyone met this test case?
Just only this case failed. How to resolve it?

Test Failed num: 4589308700496892969 Expected: 4589308704781427344 But was: 4589308704781427200

I thought calculus is for python programmers it also exist in js

Ranks can't be changed and 7kyu is the optimal rank for such tasks

The "FloatProof" test make this kata harder than 7 kyu ...

I have checked.

Your code does not pass that test because it does not return -1.

Here is the error message:

Test Failed
  num: 4503599627370497
  Expected: -1
  But was:  4503599761588225

Just tried your solution on an online compiler:

It doesn't return -1 for that input.