Write a function count_divisors(n) that returns how many positive integers divide n exactly.
For example, 12 is divisible by 1, 2, 3, 4, 6, 12, so the answer is 6.
Examples
Input: n = 12
Output: 6
Input: n = 7
Output: 2
Constraints
1 <= n <= 10**9- Your function must finish quickly even for the largest
n.
Goals
- Use `%` to test divisibility
- Avoid checking every number up to `n`