fn get_factors(n: usize) -> Vec<usize> {
    let mut flgs = vec![true; n+1];
    flgs[0] = false;
    flgs[1] = false;
    let mut factors = (0..=n).collect::<Vec<_>>();

    for i in 2..=(n as f64).sqrt().ceil() as usize {
        if !flgs[i] { continue; }
        for j in i..=n/i {
            flgs[i*j] = false;
        }
        let modval = i * i;
        for j in 1..=n/modval {
            let idx = modval*j;
            flgs[idx] = false;
            while factors[idx] % modval == 0 {
                factors[idx] /= modval;
            }
        }
    }

    factors
}

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();

    let factors = get_factors(n);
    let mut result = 0usize;
    for i in 1..=n {
        let right = factors[i];
        result += ((n / right) as f64).sqrt().floor() as usize;
    }
    println!("{}", result);
}