#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MOD = 1e9+7;

void solve() {
    ll n; cin >> n;
    ll x = n%2;
    cout << (x == 0 ? n : n-x) << endl;
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    ll t = 1;
    // cin >> t;
    while(t--) {
        solve();
    }
    return 0;
}