#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define nl "\n"
#define yes << "YES\n"
#define no << "NO\n"
#define sp " "
void solve()
{
    ll n;
    cin >> n;
    // cout<<"heo\n";
    // cout<<n;
    if (n == 1)
    {
        cout << "0";
        return;
    }
    for (int i = 2; i <= n; i++)
    {
        if (i % 2 == 0)
        {
            cout << i;
            return;
        }
    }
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    ll t = 1; // cin>>t;
    for (ll i = 0; i < t; i++)
        solve();
    return 0;
}