I just checked and the random lists can contain over 50.000 elements, so you should try another approach which requires less computation.

Please, read the instructions again, the base is always 3:

Given a positive integer N, return the largest integer k such that 3^k < N.

k is the number you have to return, and N the passed parameter.

3 < 3 is false. That's why 1 is not right, but with k = 0, 1 < 3 is true.