import java.util.*;

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