#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <ctime>
#include <cstdlib>
 
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef LL ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<ut,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=1e+5 + 1;
const ut INF=1<<29;
const ld eps=1e-6;
const LL mod=1e+6 + 3;


int main() {
	int n;
	cin >> n;
	int k = n / 2;
	int ans = 0;
	FFOR(i,1,k)FFOR(j,1,k){
		if(i + j > k)
			break;
		ans = max(ans, i * j);
	}
	cout << ans << endl;
 	return 0;
}