package no312;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		for(long i=3;i*i<=n;i++) {
			if (n % i == 0) {
				System.out.println(i);
				return;
			}
		}
		System.out.println(n);
	}
}