#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  long long n;
  cin >> n;
  n++;
  if (n == 1)
    cout << 0;
  else {
    if (n % 2 == 0)
      cout << n / 2;
    else
      cout << n;
  }
  return 0;
}
