import java.util.*;

public class Main
{
    private final static Main main = new Main();

    public static void main(String[] args)
    {
        main.contest();
    }

    private void contest()
    {
        Scanner sc = new Scanner(System.in);
        System.out.println(solve(sc.nextLong()));
    }

    private long solve(long n)
    {
        for(long i=3; i*i<=n; ++i)
        {
            if(n%i == 0)
            {
                return i;
            }
        }
        return n;
    }
}