#include "bits/stdc++.h"
#define _CRT_SECURE_NO_WARNINGS
#define rep(i,n) for(int i = 0;i < n;i++)
#define REP(i,n,k) for(int i = n;i < k;i++)
#define P(p) cout << (p) << endl;
#define sP(p) cout << setprecision(15) << fixed << p << endl;
#define vi vector<int>
#define mp(a,b) make_pair(a,b)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
int dx[] = { 1, -1 , 0 , 0};
int dy[] = { 0,  0,  1, -1};

void solve() {
  int d;
  cin >> d;
  d /= 2;
  int maxi = -1;
  rep(i,d){
    int squ = i * (d-i);
    maxi = max(maxi,squ);
  }
  P(maxi);
}

int main() {
  solve();
  return 0;
}