using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Text;
using static System.Math;
using static Extensions;
using static MathExtensions;
public static class Program
{
public static void Solve()
{
var a = I;
var max = 0;
for (var i = 1; i < a; i++) max = Max(max, i * (a - i));
Console.WriteLine(max);
}
#region Scanners
static Scanner _scanner;
static char C => _scanner.NextChar();
static string S => _scanner.NextString();
static int I => _scanner.NextInt();
static long L => _scanner.NextLong();
static BigInteger B => _scanner.NextBigInteger();
static double D => _scanner.NextDouble();
static decimal M => _scanner.NextDecimal();
#endregion
public static void Main()
{
var sw = new StreamWriter(Console.OpenStandardOutput());
sw.NewLine = "\n";
#if DEBUG
sw.AutoFlush = true;
#else
sw.AutoFlush = false;
#endif
Console.SetOut(sw);
_scanner = new Scanner(Console.OpenStandardInput());
Solve();
Console.Out.Flush();
}
}
public static partial class Extensions
{
}
#region Library
public class Scanner
{
private readonly Stream _stream;
private const int _bufferSize = 1024;
private readonly byte[] _buf = new byte[_bufferSize];
private int _len, _ptr;
public Scanner(Stream stream)
{
_stream = stream;
}
public byte ReadByte()
{
if (_ptr >= _len)
{
_len = _stream.Read(_buf, 0, _bufferSize);
_ptr = 0;
}
return _buf[_ptr++];
}
public char ReadChar() => (char)ReadByte();
public string ReadLine()
{
var r = new StringBuilder();
if (_ptr == 0) r.Append(ReadChar());
for (; _ptr < _len; _ptr++) r.Append((char)_buf[_ptr]);
return r.ToString();
}
public char NextChar() => char.Parse(NextString());
public string NextString()
{
var r = new StringBuilder();
var b = ReadChar();
while (b != ' ' && b != '\n')
{
r.Append(b);
b = ReadChar();
}
return r.ToString();
}
public int NextInt() => (int)NextLong();
public long NextLong()
{
var r = 0L;
var b = ReadByte();
var n = b == '-';
if (n) b = ReadByte();
while (b != ' ' && b != '\n')
{
r = r * 10 + b - '0';
b = ReadByte();
}
return n ? -r : r;
}
public BigInteger NextBigInteger()
{
var r = new BigInteger();
var b = ReadByte();
var n = b == '-';
if (n) b = ReadByte();
while (b != ' ' && b != '\n')
{
r = r * 10 + b - '0';
b = ReadByte();
}
return n ? -r : r;
}
public double NextDouble()
{
var i = 0L;
var b = ReadByte();
var n = b == '-';
if (n) b = ReadByte();
while (b != '.' && b != ' ' && b != '\n')
{
i = i * 10 + b - '0';
b = ReadByte();
}
if (b != '.') return n ? -i : i;
b = ReadByte();
var f = 0L;
var p = 0;
while (b != ' ' && b != '\n')
{
f = f * 10 + b - '0';
b = ReadByte();
p++;
}
var r = i + (double)f / MathExtensions.Pow(10, p);
return n ? -r : r;
}
public decimal NextDecimal() => decimal.Parse(NextString());
public T Next<T>(Converter<string, T> parser) => parser(NextString());
}
[DebuggerStepThrough]
public static partial class Extensions
{
public static void Assert(bool condition)
{
if (!condition) throw new Exception("Assertion failed");
}
public static string AsString(this IEnumerable<char> source) => new string(source.ToArray());
public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
{
foreach (var item in source) action(item);
}
public static void ForEach<T, _>(this IEnumerable<T> source, Func<T, _> func)
{
foreach (var item in source) func(item);
}
public static void ForEach<T>(this IEnumerable<T> source, Action<T, int> action)
{
var i = 0;
foreach (var item in source) action(item, i++);
}
public static void ForEach<T, _>(this IEnumerable<T> source, Func<T, int, _> func)
{
var i = 0;
foreach (var item in source) func(item, i++);
}
public static T Iterate<T>(int count, T seed, Func<T, T> func)
{
var r = seed;
Repeat(count, () => { r = func(r); });
return r;
}
public static void Repeat(int count, Action action)
{
for (var i = 0; i < count; i++) action();
}
public static void Repeat(int count, Action<int> action)
{
for (var i = 0; i < count; i++) action(i);
}
public static IEnumerable<T> Repeat<T>(Func<T> func)
{
for (var i = 0; ; i++) yield return func();
}
public static IEnumerable<T> Repeat<T>(int count, Func<T> func)
{
for (var i = 0; i < count; i++) yield return func();
}
public static IEnumerable<T> Repeat<T>(Func<int, T> func)
{
for (var i = 0; ; i++) yield return func(i);
}
public static IEnumerable<T> Repeat<T>(int count, Func<int, T> func)
{
for (var i = 0; i < count; i++) yield return func(i);
}
public static void Swap<T>(ref T x, ref T y)
{
var tmp = x; x = y; y = tmp;
}
}
[DebuggerStepThrough]
public static class MathExtensions
{
public static int Gcd(int left, int right)
{
int r;
while ((r = left % right) != 0) { left = right; right = r; }
return right;
}
public static long Gcd(long left, long right)
{
long r;
while ((r = left % right) != 0L) { left = right; right = r; }
return right;
}
public static BigInteger Gcd(BigInteger left, BigInteger right)
=> BigInteger.GreatestCommonDivisor(left, right);
public static int HighestOneBit(int x)
{
x |= x >> 01;
x |= x >> 02;
x |= x >> 04;
x |= x >> 08;
x |= x >> 16;
return x - (x >> 1);
}
public static long HighestOneBit(long x)
{
x |= x >> 01;
x |= x >> 02;
x |= x >> 04;
x |= x >> 08;
x |= x >> 16;
x |= x >> 32;
return x - (x >> 1);
}
public static int Lcm(int left, int right) => left / Gcd(left, right) * right;
public static long Lcm(long left, long right) => left / Gcd(left, right) * right;
public static BigInteger Lcm(BigInteger left, BigInteger right)
=> left / Gcd(left, right) * right;
public static int Pow(int value, int exponent)
{
var r = 1;
while (exponent > 0)
{
if ((exponent & 1) == 1) r *= value;
value *= value;
exponent >>= 1;
}
return r;
}
public static long Pow(long value, int exponent)
{
var r = 1L;
while (exponent > 0)
{
if ((exponent & 1) == 1) r *= value;
value *= value;
exponent >>= 1;
}
return r;
}
public static long Fact(int value)
{
var r = 1L;
for (var i = 2; i <= value; i++) r *= i;
return r;
}
}
#endregion