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

namespace Contest
{
    class Program
    {
        static void Main(string[] args)
        {
            ABC108.A();
        }
        
        class ABC108
        {
            public static void A()
            {
                var K = Read.Int();
                Console.WriteLine((K / 2) * ((K + 1) / 2));
            }
            public static void B()
            {
                var x1 = Read.Int();
                var y1 = Read.Int();
                var x2 = Read.Int();
                var y2 = Read.Int();
                var x3 = x2 - y2 + y1;
                var y3 = y2 + x2 - x1;
                var x4 = x3 - y3 + y2;
                var y4 = y3 + x3 - x2;
                Console.WriteLine("{0} {1} {2} {3}", x3, y3, x4, y4);
            }
            public static void C()
            {
                var N = Read.Int();
                var K = Read.Int();
                var ans = (long)(N / K) * (N / K) * (N / K);
                if (K % 2 == 0)
                {
                    var v = ((N / (K / 2)) + 1) / 2;
                    ans += (long)v * v * v;
                }
                Console.WriteLine(ans);
            }
            public static void D()
            {
                var L = Read.Int();
                List<int[]> list = new List<int[]>();
                int msb = 0;
                for(int i = 0; i < 19; ++i)
                {
                    list.Add(new int[] { i + 1, i + 2, 0 });
                    if (L >= (1 << (i + 1)))
                    {
                        list.Add(new int[] { i + 1, i + 2, 1 << i });
                        msb = i + 1;
                    }
                }
                var start = 1 << msb;
                var res = L - start;
                for(int i = 0; i < 19; ++i)
                {
                    if((res & (1 << i)) > 0)
                    {
                        list.Add(new int[] { i + 1, 20, start });
                        start += (1 << i);
                    }
                }
                Console.WriteLine("{0} {1}", 20, list.Count);
                foreach(var v in list)
                {
                    Console.WriteLine(String.Join(" ", v));
                }
            }
        }

        static class Read
        {
            static Queue<string> queue = new Queue<string>();
            static void Enqueue() { var ss = Console.ReadLine().Split(' '); foreach (var s in ss) { queue.Enqueue(s); } }
            public static int Int() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt32(queue.Dequeue()); }
            public static long Long() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt64(queue.Dequeue()); }
            public static string Str() { if (queue.Count == 0) { Enqueue(); } return queue.Dequeue(); }
            public static int[] IntN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray(); }
            public static long[] LongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray(); }
            public static string[] StrN() { return Console.ReadLine().Split(' '); }
            public static Tuple<int, int>[] TupleInt(int n) { List<Tuple<int, int>> list = new List<Tuple<int, int>>(); for (int i = 0; i < n; ++i) { var ab = Read.IntN(); list.Add(new Tuple<int, int>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<long, long>[] TupleLong(int n) { List<Tuple<long, long>> list = new List<Tuple<long, long>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<long, long>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<string, string>[] TupleStr(int n) { List<Tuple<string, string>> list = new List<Tuple<string, string>>(); for (int i = 0; i < n; ++i) { var ab = Read.StrN(); list.Add(new Tuple<string, string>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<double, double>[] TupleDouble(int n) { List<Tuple<double, double>> list = new List<Tuple<double, double>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<double, double>(ab[0], ab[1])); } return list.ToArray(); }
            public static long[,] LongMatrix(int r, int c)
            {
                var mat = new long[r, c];
                for (int i = 0; i < r; ++i)
                {
                    var x = Read.LongN();
                    for (int j = 0; j < c; ++j)
                    {
                        mat[i, j] = x[j];
                    }
                }
                return mat;
            }
            public static Dictionary<int, HashSet<int>> AdjacencyList(int N, int M)
            {
                Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
                for (int i = 0; i <= N; ++i)
                {
                    dict.Add(i, new HashSet<int>());
                }
                for (int i = 0; i < M; ++i)
                {
                    var ab = Read.IntN();
                    dict[ab[0]].Add(ab[1]);
                    dict[ab[1]].Add(ab[0]);
                }
                return dict;
            }
        }
    }
}


Measured memory_bytes: 13268