#include <iostream>
#include <math.h>
#include <stdlib.h>
using namespace std;

int main() {
  int n;
  long long int a, b;
  cin >> n;

  if (n % 2 == 0) {
    a = n / 2;
    b = n / 2;
  }
  else {
    a = n / 2;
    b = a + 1;
  }

  cout << (a + 1)*(b + 1) - 1 << endl;

  return 0;
}