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

#define endl '\n'
#define ll long long 

#define optimize() ios_base :: sync_with_stdio (0); cin.tie(0); cout.tie(0);
int main()
{
    optimize();

    int n; cin>>n;

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