Count the Divisors

**Description:** Given a positive integer n, print how many divisors it has. **Input:** One integer n (1 ≤ n ≤ 10^12). **Output:** One integer — the divisor count. **Example:** 12 → 6 (1, 2, 3, 4, 6, 12). *Careful:* looping i from 1 to n is far too slow for 10^12. Loop i while i * i <= n and count each divisor pair (i, n/i) — remember i = n/i when n is a perfect square.