use std::io;
use std::str::FromStr;
fn main() {
    let stdin = io::stdin();
    let mut buf = String::new();
    stdin.read_line(&mut buf).ok();
    let mut it = buf.split_whitespace().map(|n| usize::from_str(n).unwrap());
    let n = it.next().unwrap();
    let era = Eratosthenes::new(n as u32);
    let ans = (1..n).filter(|x| era.is_prime(*x as u32)).fold(0, |acc, x| acc + x);
    println!("{}", ans);
}

struct Eratosthenes {
    table: Vec<u32>,
}

impl Eratosthenes {
    fn new(max: u32) -> Self {
        let mut table: Vec<u32> = (0u32..=max).collect();
        for i in (2..=max).step_by(2) {
            table[i as usize] = 2;
        }
        (3u32..)
            .step_by(2)
            .take_while(|p| p * p <= max as u32)
            .for_each(|p| {
                if table[p as usize] < p {
                    return;
                }
                for x in (p..=max as u32).step_by(p as usize) {
                    table[x as usize] = p;
                }
            });
        Self { table }
    }
    fn prime_factors(&self, n: u32) -> Vec<u32> {
        let mut res = Vec::new();
        let mut now = n as usize;
        while self.table[now] != 1 {
            res.push(self.table[now]);
            now /= self.table[now] as usize;
        }
        res
    }
    fn is_prime(&self, n: u32) -> bool {
        if n == 1 {
            return false;
        }
        self.table[n as usize] == n
    }
}