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(long i = 3; i <= Math.sqrt(N); i++) {
			if(N % i == 0) {
				System.out.println(i);
				System.exit(0);
			}
		}
		if(N % 2 == 0) {
			System.out.println(N / 2);
		}else {
			System.out.println(N);
		}
		
	}
}