import java.util.*;

public class Main
{
  public static void main(String... args)
  {
    System.out.println(calc(new Scanner(System.in).nextLong()));
  }
  
  private static long calc(long n)
  {
    for(int i=3; i<(int) Math.sqrt(n); ++i)
    {
      if(n%i == 0)
      {
        return i;
      }
    }
    return n;
  }
}