Hi, here's your problem today. This problem was recently asked by AirBNB:

The power function calculates x raised to the nth power. If implemented in O(n) it would simply be a for loop over n and multiply x n times. Instead implement this power function in O(log n) time. You can assume that n will be a non-negative integer.

Here's some starting code:

```
def pow(x, n):
# Fill this in.
print(pow(5, 3))
# 125
```