import java.util.Scanner;

public class Main {

	@SuppressWarnings("resource")
	public static void main(String args[]) {
		Scanner scanner = new Scanner(System.in);
		long n=scanner.nextLong();
		for(int i=3;i<=n;i+=2) {
			if(n%i==0) {
				System.out.println(i);
				return;
			}
		}
	}
}