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

    for i in 3..=1000000 {
        if n % i == 0 {
            println!("{}", i);
            return;
        }
    }
    println!("{}", n);
}