Count Prime Numbers in a Range

You are given a positive integer n (with n > 2). Your task is to calculate the number of prime numbers in the interval \([2, n]\). A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

Formula:

\( \text{result} = \sum_{i=2}^{n} \mathbb{1}_{\text{i is prime}} \)

where \(\mathbb{1}_{\text{condition}}\) equals 1 if the condition is true, and 0 otherwise.

inputFormat

The input consists of a single line containing a positive integer n (n > 2).

outputFormat

Output a single integer representing the number of prime numbers in the range \([2, n]\).

sample

10

4