#include <bits/stdc++.h>
#define ll long long
#define pi (acos(-1))
using namespace std;
std::vector<unsigned ll> genprimevec(const unsigned ll N);
int main()
{
  int  n;
  cin>>n;
  if(n%2==0){
      cout<<n++<<endl;
return 0;  }
  cout<<n<<endl;
    return 0;
}

/*author  https://qiita.com/drken/items/0c88a37eec520f82b788*/
ll extgcd(ll a, ll b, ll &x, ll &y)
{
    if (b == 0)
    {
        x = 1, y = 0;
        return a;
    }
    ll d = extgcd(b, a % b, y, x);
    y -= a / b * x;
    return d;
}


std::vector<unsigned ll> genprimevec(const unsigned ll N)
{
    std::vector<bool> is_prime(N + 1);
    for (unsigned ll i = 0; i <= N; i++) { is_prime[i] = true; }
    std::vector<unsigned ll> P;
    for (unsigned ll i = 2; i <= N; i++)
    {
        if (is_prime[i])
        {
            for (unsigned ll j = 2 * i; j <= N; j += i) { is_prime[j] = false; }
            P.emplace_back(i);
        }
    }
    return P;
}