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