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

#define endl "\n"
#define trace(x) cout << #x << ": " << x << endl
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;
}