import java.util.Scanner;


public class Main_yukicoder312 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long n = sc.nextLong();

        for (long j = 3; j * j <= n; j++) {
        	if (n % j == 0) {
        		System.out.println(j);

        		sc.close();
        		return;
        	}
        }

        System.out.println(n);

        sc.close();
    }
}