#include <iostream>
#include <list>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdint.h>
#include <iomanip>
using namespace std;

using uint = unsigned int;
using ll = long long;

#define CIN( LL , A ) LL A; cin >> A 
#define GETSEGMENT( A , SEPARATOR ) string A; getline( cin , A , SEPARATOR ) 
#define GETLINE( A ) string A; getline( cin , A ) 
#define FOR_LL( VAR , INITIAL , FINAL_PLUS_ONE ) for( ll VAR = INITIAL ; VAR < FINAL_PLUS_ONE ; VAR ++ ) 
#define FOR_ITR( ARRAY , ITR , END ) for( auto ITR = ARRAY .begin() , END = ARRAY .end() ; ITR != END ; ITR ++ ) 
#define RETURN( LL , ANSWER ) const LL answer_for_contest = ( ANSWER ); cout << answer_for_contest << endl; return 0 
#define DOUBLE( DIGITS , ANSWER ) const double answer_for_contest = ( ANSWER ); cout << fixed << setprecision( DIGITS ) << answer_for_contest << endl; return 0 

template <typename T> inline T Distance( const T& a , const ll& b ){ return a < b ? b - a : a - b; }

int main()
{

  CIN( ll , L );
  // sum( ll i = 1 ; i <= ( L - 1 ) / 2 ; i++ ) L - ( 2 * i + 1 ) + 1
  // = sum( ll i = 1 ; i <= ( L - 1 ) / 2 ; i++ ) L - 2 * i
  // = L * ( ( L - 1 ) / 2 ) - ( ( L - 1 ) / 2 ) * ( ( L - 1 ) / 2 + 1 )
  // = ( ( L - 1 ) / 2 ) * ( L - ( L - 1 ) / 2 - 1 )
  ll L_half = ( L - 1 ) / 2;
  RETURN( ll , L_half * ( L - L_half - 1 ) );

}