#include <bits/stdc++.h>
using namespace std;
const int N = 200, M = 52 + 10, LG = 30, base = 2;
const int MOD = 1e9 + 7, mod = 1e9 + 9;
const long long INF = 1e9, inf = 1e18;
long long n, dp[N], ans;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  ;
  cin >> n;
  for (int i = 0; i < n; i++) {
    for (int j = i; j < n; j++) {
      for (int l = i; l <= j; l++) {
        dp[l]++;
      }
    }
  }
  cout << dp[n / 2];
  return 0;
}
