#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, x = 2, p, p1, sum = 0;
  cin >> n;
  p = 2;
  for (i = 3; i <= n; i++) {
    x = x + p;
    p1 = sum + x;
    x = x + p;
    p++;
    i++;
  }
  if (n == 1) {
    cout << "1";
  } else if (n == 2) {
    cout << "2";
  } else if (n % 2 == 0) {
    cout << x;
  } else {
    cout << p1;
  }
}
