import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long N = scan.nextLong();
		scan.close();
		for(int i = 3; i <= N / 2; i++) {
			if(N % i == 0) {
				System.out.println(i);
				System.exit(0);
			}
		}
		System.out.println(N);
	}
}