fn get_primes(max: usize) -> Vec<usize> {
    let mut is_prime = vec![true; max + 1];
    is_prime[0] = false;
    is_prime[1] = false;

    for n in 2.. {
        if !is_prime[n] {
            continue;
        }
        if n * n > max {
            break;
        }
        for i in ((n * n)..=max).step_by(n) {
            is_prime[i] = false;
        }
    }

    (0..=max).filter(|&n| is_prime[n]).collect()
}

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

    println!("{}", get_primes(n).into_iter().sum::<usize>());
}