import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;

class Main {
	static PrintWriter out = new PrintWriter(System.out);
	static String str;

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		long len = Long.parseLong(br.readLine());

		int i;
		double sqr=Math.sqrt(len);
		for(i=3;i<=sqr;i+=2){
			if(len%i==0){
				System.out.println(i);
				return;
			}
		}
		System.out.println(len);
	}
}