#include<iostream>
using namespace std;
typedef long long ll;
ll lcm(ll a,ll b)
{
    ll key=max(a,b);
    ll teap=key;
     while(key%a!=0||key%b!=0)
     {
         key=key+teap;
     }
     return key;
}
int main()
{
    ll n;
    while(cin>>n)
        cout<<lcm(2,n)<<"\n";
    return 0;
}
