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

public class Program
{

    public void Proc()
    {
        int[] inpt = Reader.ReadLine().Split(' ').Select(a => int.Parse(a)).ToArray();
        int num = inpt[0];
        if(num%2 == 0) {
            Console.WriteLine(num/2);
        } else {
            int ans = 0;
            for (int i = Math.Max(1,num-1); i>=1; i--) {
                int tmp1 = num - i;
                int tmp2 = num - tmp1;
                if(tmp1%i==0&&tmp2%i==0) {
                    ans = Math.Max(ans, GetGCD(tmp1, tmp2));
                }
            }
            Console.WriteLine(ans);
        }
    }

    private int GetGCD(int num1, int num2) {
        if(num1%num2 == 0) {
            return num2;
        }
        return GetGCD(num2, num1 % num2);
    }



    public class Reader
	{
		private static StringReader sr;
		public static bool IsDebug = false;
		public static string ReadLine()
		{
			if (IsDebug)
			{
				if (sr == null)
				{
					sr = new StringReader(InputText.Trim());
				}
				return sr.ReadLine();
			}
			else
			{
				return Console.ReadLine();
			}
		}
		private static string InputText = @"


21 2


";
	}

	public static void Main(string[] args)
	{
#if DEBUG
		Reader.IsDebug = true;
#endif
		Program prg = new Program();
		prg.Proc();
	}
}