#include <bits/stdc++.h>
using namespace std;
int n, m;
int i, j, k;
int main() {
  unsigned long long n;
  cin >> n;
  if (n == 0) {
    cout << "0" << endl;
    return 0;
  }
  n++;
  if (n % 2) {
    cout << n << endl;
  } else
    cout << n / 2 << endl;
  return 0;
}
