#![allow(unused_imports)]
#![allow(non_snake_case)]
use std::collections::HashMap;
use std::collections::HashSet;

#[allow(unused_macros)]
macro_rules! read {
    ([$t:ty] ; $n:expr) =>
        ((0..$n).map(|_| read!([$t])).collect::<Vec<_>>());
    ($($t:ty),+ ; $n:expr) =>
        ((0..$n).map(|_| read!($($t),+)).collect::<Vec<_>>());
    ([$t:ty]) =>
        (rl().split_whitespace().map(|w| w.parse().unwrap()).collect::<Vec<$t>>());
    ($t:ty) =>
        (rl().parse::<$t>().unwrap());
    ($($t:ty),*) => {{
        let buf = rl();
        let mut w = buf.split_whitespace();
        ($(w.next().unwrap().parse::<$t>().unwrap()),*)
    }};
}

#[allow(dead_code)]
fn rl() -> String {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).unwrap();
    buf.trim_end().to_owned()
}

fn main() {
    let n = read!(usize);

    let m = min_factor(n);
    if m == n || m >= 3{
        println!("{}", m);
    }
    else {
        for i in 3..=n {
            if n % i == 0 {
                println!("{}", i);
                return;
            }
        }
    }
}

fn min_factor(n: usize) -> usize {
    for p in primes((n as f64).sqrt() as usize + 1).iter() {
        if n % p == 0 {
            return *p;
        }
    };
    n
}

fn primes(n: usize) -> Vec::<usize> {
    if n < 2 {
        return vec![];
    }

    let mut table = vec![true; n+1];
    table[0] = false;
    table[1] = false;

    for i in 2..=(n as f64).sqrt() as usize {
        if table[i] == false {
            continue;
        }

        let mut j = i*i;
        while j <= n {
            table[j] = false;
            j += i;
        }
    }

    table
        .iter()
        .enumerate()
        .filter(|(_, &flg)| flg)
        .map(|(num, _)| num)
        .collect()
}