#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	int n; cin >> n;

	n /= 2;

	
	int ans = 0;
	for (int i = 1; i <= n; ++i) {
		int a = i;
		int b = n - i;
		ans = max(ans, a*b);
	}
	cout << ans << endl;

}