189. Count Primes

Medium · Math

Given an integer n, return the count of all prime numbers less than n.

A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

Examples

Example 1
Input: n = 10
Output: 4
Explanation: The prime numbers less than 10 are: 2, 3, 5, 7. Count = 4.
Example 2
Input: n = 2
Output: 0
Explanation: There are no prime numbers less than 2.

Constraints