using System;
using System.Collections.Generic;
using System.Linq;

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var n = long.Parse(Console.ReadLine());
            var c = true;
            for(var i = 3; i <= (long)Math.Floor(Math.Sqrt(n)); i++)
            {
                if (n % i == 0)
                {
                    Console.WriteLine(i);
                    c = false;
                    break;
                }
            }
            if (c)
            {
                if (n % 2 == 0&&n/2>2)
                {
                    Console.WriteLine(n / 2);
                }
                else
                {
                    Console.WriteLine(n);
                }
            }
        }
    }
}