#![allow(unused_imports)]

fn main() {
    input! {
        n: usize,
    }
    let m = (n as f64).sqrt() as usize;
    let mut p = vec![true; m + 1];
    p[0] = false;
    p[1] = false;
    let mut ans = 0;
    for i in 2..=m {
        if p[i] {
            for j in 2..=m / i {
                p[i * j] = false;
            }
            let mut n = n;
            let mut k = 0;
            while n >= i {
                n /= i;
                k += 1;
            }
            ans += (i.pow(k + 1) - i * i) / (i - 1);
        }
    }
    println!("{ans}");
}

use proconio::{input, marker::*};
use std::{cmp::Reverse, collections::*};

#[macro_export]
macro_rules! chmax {
    ($a:expr, $b:expr) => {{
        let tmp = $b;
        if $a < tmp {
            $a = tmp;
            true
        } else {
            false
        }
    }};
}

#[macro_export]
macro_rules! chmin {
    ($a:expr, $b:expr) => {{
        let tmp = $b;
        if $a > tmp {
            $a = tmp;
            true
        } else {
            false
        }
    }};
}

#[macro_export]
/// mvec![]
macro_rules! mvec {
    ($val:expr; ()) => {
        $val
    };
    ($val:expr; ($size:expr $(,$rest:expr)*)) => {
        vec![mvec![$val; ($($rest),*)]; $size]
    };
}