#include<bits/stdc++.h>
using namespace std;
#define int long long
#define INF 1e9 + 7
#define endl '\n'
#define bug(a) cout << #a << " : " << a << '\n';

void solve(int cs){

}

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

    int n;cin >> n;
    if(n % 2 == 0) cout << n << endl;
    else cout << n-1 << endl;
    
    
    return 0;
}