import java.util.*;

public class Main {
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		
		for(int i=3;i*i<=n;i++){
			if(n%i==0){
				System.out.println(i);
				return;
			}
		}
		System.out.println(n);
	}
}