Given an integer n, return the number of prime numbers that are strictly less than n.
Example 1:
Input: n = 10 Output: 4 Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7.
Example 2:
Input: n = 0 Output: 0
Example 3:
Input: n = 1 Output: 0
Constraints:
0 <= n <= 5 * 106