import java.util.*;

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