What is wrong with doing it mathematically?

#1

long res = (long) Math.floor(Math.exp(Math.log(n)/k));

This is the solution I deduced after mathematical calculations. However, it is not passing the third test. What is wrong with this logic?

#2

So the tester is giving “Wrong Answer” for 3rd test case. However, when I checked it after downloading the test cases input and output, it is showing the same answer as the output file.

#3

no for test case
1000000000000 4

you are getting
999

whereas the answer should be 1000