#include<bits/stdc++.h>
using namespace std;

int n;
int ans;
int memo[11111][11111];

void solve(int a, int b){

  if(a*2+b*2 > n) return;
  if(~memo[a][b]) return;
  ans = max(ans, a * b);  

  memo[a][b] = a * b;
  
  solve(a+1, b);
  solve(a, b+1);
  
  return;
}

int main(){

  cin >> n;

  memset(memo, -1, sizeof(memo));
  solve(0, 0);
  cout << ans << endl;

}