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

class Program
{
    public void Proc()
    {
        Reader.IsDebug = false;
        long num = long.Parse(Reader.ReadLine());
        Dictionary<long, long> tmp = this.CreateDic(num);
        long ans = num;
        if(tmp.ContainsKey(2) && tmp[2] >= 2) {
            ans = 4;
        }
        ans = Math.Min(ans, tmp.Keys.Where(a=>a>2).Min());
        Console.WriteLine(ans);
    }
    
    private Dictionary<long, long> CreateDic(long num) {
        long tmp = num;
        Dictionary<long, long> ret = new Dictionary<long, long>();
        for(int i=2; i*i<=num; i++) {
            while (tmp % i == 0)
            {
                if(ret.ContainsKey(i)) {
                    ret[i]++;
                } else {
                    ret.Add(i, 1);
                }
                tmp = tmp / i;
            }
            if(tmp == 1) {
                break;
            }
        }
        if(tmp > 1) {
            ret.Add(tmp, 1);
        }
        return ret;
        
    }
    
    
    


    public class Reader
    {
        public static bool IsDebug = true;
        private static String PlainInput = @"




8573912969


 
";
        private static System.IO.StringReader Sr = null;
        public static string ReadLine()
        {
            if (IsDebug)
            {
                if (Sr == null)
                {
                    Sr = new System.IO.StringReader(PlainInput.Trim());
                }
                return Sr.ReadLine();
            }
            else
            {
                return Console.ReadLine();
            }
        }
    }
    static void Main()
    {
        Program prg = new Program();
        prg.Proc();
    }
}