#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;

int main(){
    int n;
    cin >> n;
    if (!(n%2)) cout << n+1 << endl;
    else cout << n << endl;
}