using System;

class Program
{
    static void Main()
    {
        long n = long.Parse(Console.ReadLine());

        long ans = 0;

        for (long i = 3; i * i <= n; i++)
        {
            if (n % i == 0)
            {
                ans = i;
                break;
            }
        }
        if (ans == 0) ans = n;

        Console.WriteLine(ans);
    }
}