using System;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        int L = int.Parse(Console.ReadLine());
        long kaibunCnt = 0;

        for (int i = 0; i <= L - 2; i += 2)
        {
            kaibunCnt += (L - i) / 2;             // aba
            kaibunCnt += (L - i - 1) / 2 - 1;     //bab
        }
        Console.WriteLine(kaibunCnt);
    }
}