using System;
using System.Collections.Generic;
using System.Text;
using sc = Scanner;
using System.Collections;
using System.Linq;


class Program
{
    static void Main(string[] args)
    {
        Solve();

#if DEBUG
        Console.WriteLine("終了するにはなにかキーを押して下さい...");
        Console.ReadKey();
#endif

    }

    static void Solve()
    {
        int d = sc.NextInt();
        if (d < 4)
        {
            Console.WriteLine(0);
            return;
        }

        int allowedUse = (d - (d % 2))/2;
        int low = 0;
        int hi = allowedUse;
        int right, left; // if you need, change other Type (ex. long, Biginteder)

        while (hi > low + 2)
        {
            left = (2 * low + hi) / 3;
            right = (low + 2 * hi) / 3;

            if (f(allowedUse - left,left) > f(allowedUse - right,right))//f(left) , f(right) change f for comparison.
            {
                hi = right;
            }
            else
            {
                low = left;
            }
        }
        //answer is (low+hi)/2;
        Console.WriteLine(f(allowedUse - (low + hi) / 2, (low + hi) / 2));

#if DEBUG
        Console.WriteLine("local check"); // Visual Studioのローカル変数チェック用
#endif 
    }

    static int f(int a, int b)
    {
        return a * b;
    }


 }



public static class Scanner
{
    public static string[] NextStrArray()
    {
        return Console.ReadLine().Split(' ');
    }

    public static long[] NextLongArray()
    {
        string[] s = NextStrArray();
        long[] a = new long[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = long.Parse(s[i]);
        }
        return a;
    }
    public static int[] NextIntArray()
    {

        string[] s = NextStrArray();
        int[] a = new int[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = int.Parse(s[i]);
        }
        return a;
    }
    public static int NextInt()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return int.Parse(tmp);
    }
    public static double NextDouble()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return double.Parse(tmp);
    }
    public static long NextLong()
    {
        string tmp = "";
        while (true)
        {
            string readData = char.ConvertFromUtf32(Console.Read());
            if (readData == " " || readData == "\n")
                break;
            tmp += readData;
        }
        return long.Parse(tmp);
    }
    public static double[] NextDoubleArray()
    {

        string[] s = NextStrArray();
        double[] a = new double[s.Length];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = double.Parse(s[i]);
        }
        return a;
    }
}