use std::io::*;
fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let m = (n as f64).sqrt() as usize;
    let mut is_prime: Vec<bool> = vec![true; m + 1];
    let mut ps = Vec::new();
    is_prime[0] = false;
    is_prime[1] = false;
    for i in 2..m + 1 {
        if is_prime[i] {
            ps.push(i);
            let mut j = i * 2;
            while j <= m {
                is_prime[j] = false;
                j += i;
            }
        }
    }

    let mut ans = 0usize;
    let mut val: Vec<usize> = (0..n + 1).collect();
    for &p in ps.iter() {
        let p2 = p * p;
        for i in 1..n / p2 + 1 {
            while val[i * p2] % p2 == 0 {
                val[i * p2] /= p2;
            }
        }
    }
    for i in 1..n + 1 {
        // val[i] * x <= nの平方数xの数
        ans += (n as f64 / val[i] as f64).sqrt() as usize;
    }
    println!("{}", ans);
}