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