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

int main(void) {
	int N;
	cin >> N;
	
	N /= 2;
	int ans = 0;
	for(int i = 1; i <= N; ++i) ans = max(ans, i * (N - i));
	
	cout << ans << "\n";
	
	return 0;
}