fn main() {
    let x: u64 = input_a_value();
    let mut v = prime_factors(x);

    if v.len() < 2 {
        println!("0");
        return;
    }

    let a = v.pop().unwrap();
    let b = v.iter().fold(0, |acc, x| acc + x);
    println!("{}", a + b);
}
fn input_a_value<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn prime_factors(num: u64) -> Vec<u64> {
    let mut result = num;

    for i in 2..(num as f64).sqrt().ceil() as usize {
        if num % i as u64 == 0 {
            result = i as u64;
            break;
        }
    }

    if result == num {
        vec![num]
    } else {
        let mut v_1 = vec![result];
        let mut v_2 = prime_factors(num / result);
        v_1.append(&mut v_2);
        v_1
    }
}