using System;
using System.Linq;
class Program {
  public static void Main() {
    int N = int.Parse(Console.ReadLine());
    int[] a = new int[N];
    for(int i = 0; i < N; ++i) {
      a[i] = i;
    }
    int res = (N + 1) / 2;
    int key = 100000;
    int val = N / (a.Length - N);
    res += (val + 1) * (val + 1);
    res -= val * val + 2 * val + 1;
    Console.WriteLine(res);
  }
}