using System;

public class Hello
{
    static void Main()
    {
        var n = long.Parse(Console.ReadLine().Trim());
        getAns(n);
    }
    static void getAns(long n)
    {
        for (long i = 3; i * i <= n; i++)
        {
            if (n % i == 0) { Console.WriteLine(i); return; }
        }
        Console.WriteLine(n % 2 == 0 && n / 2 > 2 ? n / 2 : n);
    }
}