import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long n=sc.nextLong();
		long ans=0;
		for(int i=3;i<=Math.sqrt((double)n);i++){
			if(n%i==0){
				ans=i;
				break;
			}
		}
		if(ans==0){
			if(n%2==0&&n/2!=2){
				ans=n/2;
			}else{
				ans=n;
			}
		}
		System.out.println(ans);

	}
}