#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>

using namespace std;


int main(){
	long long d;
	cin >> d;
	long long ans = 0;
	for(int x = 1; 2*x <= d/2; x++){
		long long y = (d - 2*x)/2;
		ans = max(ans, x*y);
	}
	cout << ans << endl;
	return 0;
}