#include <bits/stdc++.h>
using namespace std;
 
typedef long long int ll;
typedef unsigned long long int ull;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef pair<ll, ll> pi;
typedef pair<char, ll> pci;
typedef vector<pi> vii;
typedef map<ll, ll> mi;
typedef map<char, ll> mci;
typedef set<ll> seti;
typedef set<char> setc;
typedef unordered_set<ll> useti;
typedef unordered_set<char> usetc;
 
#define sz size()
#define ins insert
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define nl << "\n";
#define NO cout << "NO" nl
#define YES cout << "YES" nl
#define all(x) x.begin(), x.end()
#define db(x) cout << #x << " = " << x nl
#define input(x) for (auto &a : x) cin >> a;
#define view(x) cout << #x << ": "; for (auto &a : x) {cout << a << " ";} cout nl
#define viewp(x) cout << #x << ": "; for (auto &a : x) {cout << "{" << a.first << ", " << a.second << "} ";} cout nl
 
void solve(){
	ll n;
	cin >> n;
	cout << n - (n % 2) nl
}

int main() {
	ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
	cout.tie(nullptr);
	ll t = 1;
	//cin >> t;
	while (t--) {
		solve();
	}
    return 0;
}