#include<bits/stdc++.h>
using namespace std;

#define nl '\n'
#define ll long long
#define int long long
#define pii pair<int, int> 



void solve(){
    int n; cin >> n;
    cout << n - (n&1) << nl;
}

int32_t main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int t = 1, tc = 0;
    // cin >> t ;
    while(t--){
        // cout << "Case " << ++tc  << ": ";
        solve();
    }
    return 0;
}