Count Of Prime Numbers Till N

You are given an integer n. You need to find out the number of prime numbers in the range [1, n] (inclusive). Return the number of prime numbers in the range.

A prime number is a number which has no divisors except, 1 and itself.

Example 1

Input : n = 6
Output : 3
Explanation :
Prime numbers in the range [1, 6] are 2, 3, 5.

Example 2

Input : n = 10
Output : 4
Explanation :
Prime numbers in the range [1, 10] are 2, 3, 5, 7.

Example 3

Input : n = 20
Output : 8

Constraints

• 2 <= n <= 1000