import java.util.*;

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