#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  if (n == 0) {
    cout << "0" << endl;
  } else {
    if ((n + 1) % 2 == 0) {
      cout << (n + 1) / 2 << endl;
    } else {
      cout << n + 1 << endl;
    }
  }
}
