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