import java.util.*;
import java.io.*;

public class Exercise75{
  public static void main (String[] args) throws IOException{

    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    String nStr = new String(in.readLine());

    long n = Long.parseLong(nStr);

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

    System.out.println(n);
  }
}