#include <bits/stdc++.h>
using namespace std;
bool prime[1000005];
const int MaxN = 2e5 + 10;
const int MAXN = 120 * 1000;
long long n, sum = 0, i, h = 1000000000007, t, a, b, m, r, ans = 0;
int x, y, z;
vector<pair<int, int>> p;
vector<long long> v;
string s = "VIB";
string s1 = "GYOR";
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n;
  n++;
  cout << ((n + 1) / 2) * (n / 2);
  return 0;
}
